Calling Thomistic Philosophers: Induction and a posteriori demonstration

[Blue_Horizon]

Aquinas’s discussion on certainty re the existence of “God” by reason alone in SCG had me thinking.

Aquinas asserts that certain knowledge of a cause can be had (demonstrated) from knowledge of its effects. Aquinas calls such inferences “a posteriori.”
Modern understanding of induction/deduction suggests that such an a posteriori demonstration is in fact inductive.
If the knowledge of the cause is through induction then its truth is only probable (as the case of “William’s Chicken” shows*).

How then can Thomas teach that such knowledge of the existence of God is “certain” rather than “probable”?

• Williams’s Chicken:
  The farmer’s wife comes out the back door every morning to feed grain to her chickens. Hence the chickens come running. After many months she comes out the back door and strangles the first chicken that reaches her. (Unbeknown to the chickens it was Christmas day.)

 

[AuditVocemMeam]

By induction I am imagining something like, “we have these data; we postulate this cause as an explanation for these data; if we assume this cause, the data are explained in a rational manner.” If you are referring to something else, please correct me.

Aquinas’ metaphysical arguments are a posteriori in the sense that they require certain principles derived from experience and not achievable from pure reason alone. Thus the “motion” argument, or the First Way, depends on the premise that certain things change, or that certain potencies (capacities for change) are actualized (brought into being). If it were not known that things change, then this argument would be impossible to make. But it can only be known that things change by experience of the change, not from pure reason. This is how this argument is a posteriori.

But once this premise is granted, that certain potencies are actualized (along with an understanding of being, act, potency, and causality), the rest of the argument is deductive. A potency, since it is only a capacity to be actualized, is not in act, and therefore cannot actualize itself since something must be actually in order to have any causal power. If a potency actualized itself, it would not actually exist but would yet cause something. It would, in fact, cause itself to come into existence, which is absurd since “to cause itself to come into existence” implies that before the causation, the thing did not exist, and something which does not exist cannot cause anything.

So we have two premises:

1. There are some potencies which are actualized.
2. Every potency which is actualized must be actualized by something else which is in act.

The rest of the argument flows from these premises as a deduction. The argument is not inductive in the sense of “we have these data; let us postulate God as an explanation for these data.” It is an attempt to show that these premises lead certainly and inescapably to the conclusion that there must be some being which is Pure Act, without which no potency could be actualized and, equivalently, nothing could change. So the argument does have an a posteriori component which is the understanding that things do, in fact, change, since we could not know this unless we experienced it. But once the (very basic) a posteriori premise is granted, the rest is from deduction, and, if it is done properly, and I think it is, the argument is infallible like all other correct deductive reasoning.

 

[Blue_Horizon]

By induction I am imagining something like, "we have these data; we postulate this cause as an explanation for these data; if we assume this cause, the data are explained in a rational manner."
[BH]: Yes I think this is a good starting definition - though “principle” or “rule” may be a better word than “assumed cause”.

Aquinas’ metaphysical arguments are a posteriori in the sense that they require certain principles derived from experience and not achievable from pure reason alone.
[BH]: Yes I am with you so far but this may need to be precisioned a little more…

**Thus the “motion” argument, or the First Way, depends on the premise that certain things change, or that certain potencies (capacities for change) are actualized (brought into being). **
[BH]: I think this may have speed wobbles. One does not seem to need to do repeated empirical tests or observations to prove the truth of this principle (that some potentialities are actualized). So this looks more like an “analytic” truism (like “all bachelor’s are unmarried”), i.e. it is true because a relationship between subject and predicate is inherent in the definition of the words used. One does not really need to investigate a couple of hundred bachelors to discover this principle. The paired “potentiality/actuality” concepts appear to cross-contaminate at the very level of definition even before we look at real-world examples.

If this is indeed an “analytic” type truism (as opposed to a synthetic one) then it must be an “a priori” proposition because it is well known that analytic “a posteriori” truths are self-contradictory and hence non-existant (Kant).

**So we have two premises:

1. There are some potencies which are actualized.
2. Every potency which is actualized must be actualized by something else which is in act.**
   [BH] If I am correct above then both these premises are “a priori”.
   Yet Aquinas says proofs from effect to cause are “a posteriori.”

Have we missed something?

 

[Rhubarb]

Does modern understanding of induction/deduction suggest that an a posteriori demonstration is inductive?

I was taught that induction relates to a priori relates to analytic propositions relates to rationalism; while deduction relates to a posteriori relates to synthetic propositions relates to empiricism.

I haven’t read the text of Aquinas in some years but if I had to break down the essence of the First Way, as I recall and understand it, I would say this: Through what I have learned and therefore know, a posteriori, about motion I can deduce that there must be some unmoved force from which movement springs - to prevent an infinite regress of motion.

 

[Blue_Horizon]

Rhubarb:

I was taught that induction relates to a priori relates to analytic propositions relates to rationalism; while deduction relates to a posteriori relates to synthetic propositions relates to empiricism.

Can you expand on this?

… if I had to break down the essence of the First Way, as I recall and understand it, I would say this: Through what I have learned and therefore know, a posteriori, about motion I can deduce that there must be some unmoved force from which movement springs - to prevent an infinite regress of motion./

Actually I think this falls over re the First Way because we now know Aristotle/Aquinas completely misunderstood a posteriori motion and inertia - at least inso far as they thought they knew about it by observing the world (especially the physical motion of the celestial spheres which this First Way appears to be empirically based upon).

Aquinas thought a body in motion would grind to a halt unless acted upon by an external mover/force. Newtonian physics teaches this is false. An object will remain in motion if left unaided. If it is acted upon it will either accelerate or slow down. A poor choice of worldly analogy/example by Aquinas even if his metaphysical principle is correct.

It seems his philosophic definition of “motion” here (if the principle is correct) then cannot be the same one as that of the celestial spheres.
And if his philosophic motion principle is correct then it must be apriori not aposteriori because his empirical example/induction from which he allegedly derives it actually fails.

 

[Prodigal_Son]

I was taught that induction relates to a priori relates to analytic propositions relates to rationalism; while deduction relates to a posteriori relates to synthetic propositions relates to empiricism.

You’re confusing induction and deduction here. Deduction is a priori. Induction is a posteriori.

 

[hicetnunc]

For St Thomas, demonstrative reasoning moves either from cause to effect (a priori), or from the effect to the cause (a posteriori: see ST 1a, q.2, a2). Both can yield certain conclusions, because one can arrive at knowledge of causes through an understanding of effects, or an understanding of effects through knowledge of the cause. In his commentary on Aristotle’s Posterior Analytics (especially book 1), he says that the inductive move from effect to cause is the way in which scientific knowledge is acquired. A priori and a posteriori knowledge are thus not two distinct kinds of knowledge, but simply two methods of demonstration. Once you have demonstrated a cause from an effect, you can then demonstrate the effect from the cause by way of methodical verification. For this reason, Thomas does not think that demonstrating the existence of God is a matter of faith, but what he calls a “preamble of faith”, because the light of natural reason can make the connection between effects and causes and vice versa.

The modern distinction between inductive and deductive reasoning was inherited from Enlightenment philosophers (especially the empiricists like Hume) who considered induction and deduction to be two different kinds of knowledge, one being ‘certain’ the other ‘probable’. Pope John Paul II tackled this modern dichotomy in both Veritas Splendor and Fides et Ratio.

For Thomas, all knowledge begins in sense experience, but does not end there; one can draw certain metaphysical conclusions using the inductive method, because correct inductive reasoning moves beyond what is poeterior (the effect) to what is prior (the cause) and therefore certain.

 

[SextusEmpiricus]

Actually I think this falls over re the First Way because we now know Aristotle/Aquinas completely misunderstood a posteriori motion and inertia - at least inso far as they thought they knew about it by observing the world (especially the physical motion of the celestial spheres which this First Way appears to be empirically based upon).

Aquinas thought a body in motion would grind to a halt unless acted upon by an external mover/force. Newtonian physics teaches this is false. An object will remain in motion if left unaided. If it is acted upon it will either accelerate or slow down. A poor choice of worldly analogy/example by Aquinas even if his metaphysical principle is correct.

It seems his philosophic definition of “motion” here (if the principle is correct) then cannot be the same one as that of the celestial spheres.
And if his philosophic motion principle is correct then it must be apriori not aposteriori because his empirical example/induction from which he allegedly derives it actually fails.

This is not entirely accurate. When Aquinas uses the term “motion,” he is referring to any kind of change, not just physics, celestial spheres, etc.

 

[Rhubarb]

You’re confusing induction and deduction here. Deduction is a priori. Induction is a posteriori.

Darn. I dis get them backwards. That’s what I get for posting past midnight.

 

[Blue_Horizon]

This is not entirely accurate. When Aquinas uses the term “motion,” he is referring to any kind of change, not just physics, celestial spheres, etc.

SE yes I agree that “local motion” is, for Aquinas, one of the types of change that his generic definition of “motion” is meant to encompass.

However the observation I am making is that, by doing experiments (ie aposteriori) “local motion” does not in fact inductively prove his bigger philosophic principle of “motion”.

Aquinas thought observation of local motion (the celestial spheres, arrows etc) did support his motion principle.

Does his bigger philosophic principle of “motion” still stand then?
Yes it may well stand in other areas of change - but not when talking about change in speed.

Is his philosophic principle of “motion” proven aposteriori or apriori? I do not know. Induction from local motion appears seriously flawed. His principle of “motion” (as opposed to local motion) may well be justified apriori.

In that case we may as well forget the First Way and deal with the far meatier proofs from contingency and potency/act which are philosophically closer to what he really means than are contradicting laws derived from “local motion.” But I will argue these may be apriori anyway. I believe the whole point of the First Way is to inductively prove the existence of an unmoved mover from aposteriori principles to do with local motion.

What other “motion” examples are there from the real-world if “local motion” falls over?
And are they truly a posteriori?

The attached article deals very thoroughly with possible solutions to this conundrum.
Though I think there are still some holes in the arguments presented.

 

[Blue_Horizon]

For St Thomas, demonstrative reasoning moves either from cause to effect (a priori), or from the effect to the cause (a posteriori: see ST 1a, q.2, a2). Both can yield certain conclusions, because one can arrive at knowledge of causes through an understanding of effects, or an understanding of effects through knowledge of the cause. In his commentary on Aristotle’s Posterior Analytics (especially book 1), he says that the inductive move from effect to cause is the way in which scientific knowledge is acquired. A priori and a posteriori knowledge are thus not two distinct kinds of knowledge, but simply two methods of demonstration. Once you have demonstrated a cause from an effect, you can then demonstrate the effect from the cause by way of methodical verification. For this reason, Thomas does not think that demonstrating the existence of God is a matter of faith, but what he calls a “preamble of faith”, because the light of natural reason can make the connection between effects and causes and vice versa.

The modern distinction between inductive and deductive reasoning was inherited from Enlightenment philosophers (especially the empiricists like Hume) who considered induction and deduction to be two different kinds of knowledge, one being ‘certain’ the other ‘probable’. Pope John Paul II tackled this modern dichotomy in both Veritas Splendor and Fides et Ratio.

For Thomas, all knowledge begins in sense experience, but does not end there; one can draw certain metaphysical conclusions using the inductive method, because correct inductive reasoning moves beyond what is poeterior (the effect) to what is prior (the cause) and therefore certain.

Hi H&H. A nice summary of the Scholastic framework. The problem is one aspect doesn’t ring true - hence the Enlightenment critiques. The problem area is where you opine:

“demonstrative reasoning moving … from the effect to the cause (aposteriori).”
“A priori and a posteriori knowledge are thus not two distinct kinds of knowledge, but simply two methods of demonstration…Both can yield certain conclusions.”

We all agree these are two methods of demonstration.
But what is your basis for being certain they are not distinct kinds of knowledge?
As above “William’s Chicken” (an example of induction) clearly shows induction provides probability not certainty. Of course induction may not be the same as aposteriori.

“Aristotle…says that the inductive move from effect to cause.”

You have conflated both induction (Aristotle) and aposteriori (Aquinas) as if they are exactly the same thing. But are they? I don’t think so.

Can you explain why you believe aposteriori demonstration can provide certainty when actual induction (William’s Chicken) does not?

 

[SextusEmpiricus]

SE yes I agree that “local motion” is, for Aquinas, one of the types of change that his generic definition of “motion” is meant to encompass.

However the observation I am making is that, by doing experiments (ie aposteriori) “local motion” does not in fact inductively prove his bigger philosophic principle of “motion”.

Aquinas thought observation of local motion (the celestial spheres, arrows etc) did support his motion principle.

Does his bigger philosophic principle of “motion” still stand then?
Yes it may well stand in other areas of change - but not when talking about change in speed.

Is his philosophic principle of “motion” proven aposteriori or apriori? I do not know. Induction from local motion appears seriously flawed. His principle of “motion” (as opposed to local motion) may well be justified apriori.

In that case we may as well forget the First Way and deal with the far meatier proofs from contingency and potency/act which are philosophically closer to what he really means than are contradicting laws derived from “local motion.” But I will argue these may be apriori anyway. I believe the whole point of the First Way is to inductively prove the existence of an unmoved mover from aposteriori principles to do with local motion.

What other “motion” examples are there from the real-world if “local motion” falls over?
And are they truly a posteriori?

The attached article deals very thoroughly with possible solutions to this conundrum.
Though I think there are still some holes in the arguments presented.

Again, I think you are misunderstanding Aquinas, specifically his concept of “motion.” Newton’s theories have no impact on Aquinas because they are grounded in science, while Aquinas’s theories are grounded in philosophy (more specifically, metaphysics). Thus, the veracity of Aquinas’s First proof (that nothing can move itself) does not depend on Newton’s first law of motion.

 

[Blue_Horizon]

Again, I think you are misunderstanding Aquinas, specifically his concept of “motion.” Newton’s theories have no impact on Aquinas because they are grounded in science, while Aquinas’s theories are grounded in philosophy (more specifically, metaphysics). Thus, the veracity of Aquinas’s First proof (that nothing can move itself) does not depend on Newton’s first law of motion.

SE I think you need to tease this out.
Isn’t it simply an unexplained assertion on your part to say Aquinas’s theories are grounded in “philosophy (metaphysics)” while Newton’s are grounded in “Science.”

If Aquinas asserts that his demonstration starts with “a posteriori” demonstrations (some here equate this with induction) then Aquinas is surely starting from truths he thinks are manifested/derived from sensible local motion?

If you opine it isn’t just from sensible “local motion” then it must be some other form of sensible “motion.” Can you provide an example if its not local motion?

The attached article may (or may not) assist as it better describes the difficulties I see.

 

[Linusthe2nd]

By induction I am imagining something like, “we have these data; we postulate this cause as an explanation for these data; if we assume this cause, the data are explained in a rational manner.” If you are referring to something else, please correct me.

Aquinas’ metaphysical arguments are a posteriori in the sense that they require certain principles derived from experience and not achievable from pure reason alone. Thus the “motion” argument, or the First Way, depends on the premise that certain things change, or that certain potencies (capacities for change) are actualized (brought into being). If it were not known that things change, then this argument would be impossible to make. But it can only be known that things change by experience of the change, not from pure reason. This is how this argument is a posteriori.

But once this premise is granted, that certain potencies are actualized (along with an understanding of being, act, potency, and causality), the rest of the argument is deductive. A potency, since it is only a capacity to be actualized, is not in act, and therefore cannot actualize itself since something must be actually in order to have any causal power. If a potency actualized itself, it would not actually exist but would yet cause something. It would, in fact, cause itself to come into existence, which is absurd since “to cause itself to come into existence” implies that before the causation, the thing did not exist, and something which does not exist cannot cause anything.

So we have two premises:

1. There are some potencies which are actualized.
2. Every potency which is actualized must be actualized by something else which is in act.

The rest of the argument flows from these premises as a deduction. The argument is not inductive in the sense of “we have these data; let us postulate God as an explanation for these data.” It is an attempt to show that these premises lead certainly and inescapably to the conclusion that there must be some being which is Pure Act, without which no potency could be actualized and, equivalently, nothing could change. So the argument does have an a posteriori component which is the understanding that things do, in fact, change, since we could not know this unless we experienced it. But once the (very basic) a posteriori premise is granted, the rest is from deduction, and, if it is done properly, and I think it is, the argument is infallible like all other correct deductive reasoning.

Very good. LInus2nd

 

[Linusthe2nd]

Again, I think you are misunderstanding Aquinas, specifically his concept of “motion.” Newton’s theories have no impact on Aquinas because they are grounded in science, while Aquinas’s theories are grounded in philosophy (more specifically, metaphysics). Thus, the veracity of Aquinas’s First proof (that nothing can move itself) does not depend on Newton’s first law of motion.

Good point. And often overlooked. Linus2nd

 

[SextusEmpiricus]

SE I think you need to tease this out.
Isn’t it simply an unexplained assertion on your part to say Aquinas’s theories are grounded in “philosophy (metaphysics)” while Newton’s are grounded in “Science.”

If Aquinas asserts that his demonstration starts with “a posteriori” demonstrations (some here equate this with induction) then Aquinas is surely starting from truths he thinks are manifested/derived from sensible local motion?

If you opine it isn’t just from sensible “local motion” then it must be some other form of sensible “motion.” Can you provide an example if its not local motion?

The attached article may (or may not) assist as it better describes the difficulties I see.

There is no need to “tease” anything, particularly if you continue to insist that Newton and Aquinas mean the same thing when they use the term “motion.”

 

[hicetnunc]

Hi BlueHorizon;
Thanks for your reply and thoughts.

The problem area is where you opine: “demonstrative reasoning moving … from the effect to the cause (aposteriori).” “A priori and a posteriori knowledge are thus not two distinct kinds of knowledge, but simply two methods of demonstration…Both can yield certain conclusions.”

This is not me “opining”. You asked about what St Thomas teaches, and this is what he holds in respect to the relationship between a priori and a posteriori knowledge. The fact that Enlightenment philosophers rejected this framework is well-documented and much-discussed by philosophers (see for example, A. MacIntyre’s, Three Rival Versions of Moral Inquiry, and J. Knasas, Being & Some 20th Century Thomists). This is the fundamental difference between the Scholastic and Enlightenment understanding of a posteriori and a priori reasoning.

We all agree these are two methods of demonstration. But what is your basis for being certain they are not distinct kinds of knowledge?

Knowledge for Aquinas is the possession of the truth; there can be no such thing as false knowledge. What is known is determined by its object, not by its method. So Thomas distinguishes between practical and speculative knowledge, since these have different objects. But the method by which we arrive at the knowledge of something does not alter the truth of it. For example, you could arrive at the knowledge of a weight either inductively or deductively; but given that the answer is the same, there is no difference in the kind of knowledge gained, but only in the method by which the knowledge was gained. Where there is a difference in knowledge is where there is a difference in the object of knowledge, whether something is known for the sake of something else or for its own sake. We could also have knowledge of contingent and necessary things; for example, the knowledge that I am sitting know does not appear to be the same kind of knowledge that 2 + 2 = 4. But in both cases, something is known which is true, and could be known through different methods. The only difference is that contingent things are sometimes true, whereas absolutely necessary things are always true. But the object—truth—is the same and what determines knowledge.

I think where confusion arises in mixing up reasoning with knowledge. There are different kinds of reasoning, some which yield the truth, and some which do not. Thus, not all reasoning leads to certainty; but all knowledge, by definition, is certain.

You have conflated both induction (Aristotle) and aposteriori (Aquinas) as if they are exactly the same thing. But are they? I don’t think so.

I don’t believe I have. Thomas uses both terms, and borrows them from Aristotle’s use of the Greek term epagogue which he variously translates into Latin as a posteriori and induction (for example, in the Commentary on Posteriori Analytics 1.1.n10, “manifestat propositionem praemissam per inductionem”).

Can you explain why you believe aposteriori demonstration can provide certainty when actual induction (William’s Chicken) does not?

I’m not sure what you think your chicken is supposed to be demonstrating, but from an Aristotelian/Thomist point of view, all it shows is that the chickens had a mistaken belief about why they were being called by the farmer’s wife. In Aristotelian/Thomistic philosophy (in fact, all philosophy until the Enlightenment) there is a distinction between a right opinion and a wrong opinion (Socrates is at pains to draw this distinction out in Plato’s dialogues, such as Meno). The chickens simply had a wrong opinion, but not knowledge.

 

[Linusthe2nd]

Hi BlueHorizon;
Thanks for your reply and thoughts.

This is not me “opining”. You asked about what St Thomas teaches, and this is what he holds in respect to the relationship between a priori and a posteriori knowledge. The fact that Enlightenment philosophers rejected this framework is well-documented and much-discussed by philosophers (see for example, A. MacIntyre’s, Three Rival Versions of Moral Inquiry, and J. Knasas, Being & Some 20th Century Thomists). This is the fundamental difference between the Scholastic and Enlightenment understanding of a posteriori and a priori reasoning.

Knowledge for Aquinas is the possession of the truth; there can be no such thing as false knowledge. What is known is determined by its object, not by its method. So Thomas distinguishes between practical and speculative knowledge, since these have different objects. But the method by which we arrive at the knowledge of something does not alter the truth of it. For example, you could arrive at the knowledge of a weight either inductively or deductively; but given that the answer is the same, there is no difference in the kind of knowledge gained, but only in the method by which the knowledge was gained. Where there is a difference in knowledge is where there is a difference in the object of knowledge, whether something is known for the sake of something else or for its own sake. We could also have knowledge of contingent and necessary things; for example, the knowledge that I am sitting know does not appear to be the same kind of knowledge that 2 + 2 = 4. But in both cases, something is known which is true, and could be known through different methods. The only difference is that contingent things are sometimes true, whereas absolutely necessary things are always true. But the object—truth—is the same and what determines knowledge.

I think where confusion arises in mixing up reasoning with knowledge. There are different kinds of reasoning, some which yield the truth, and some which do not. Thus, not all reasoning leads to certainty; but all knowledge, by definition, is certain.

I don’t believe I have. Thomas uses both terms, and borrows them from Aristotle’s use of the Greek term epagogue which he variously translates into Latin as a posteriori and induction (for example, in the Commentary on Posteriori Analytics 1.1.n10, “manifestat propositionem praemissam per inductionem”).

I’m not sure what you think your chicken is supposed to be demonstrating, but from an Aristotelian/Thomist point of view, all it shows is that the chickens had a mistaken belief about why they were being called by the farmer’s wife. In Aristotelian/Thomistic philosophy (in fact, all philosophy until the Enlightenment) there is a distinction between a right opinion and a wrong opinion (Socrates is at pains to draw this distinction out in Plato’s dialogues, such as Meno). The chickens simply had a wrong opinion, but not knowledge.

Very interesting. So " induction " and " a posteriori " reasoning are the same for Thomas. Is that correct? But because of Hume or at least the Enlightenment the meaning of " induction " has changed, is that correct? So in discussions we should ask what exactly how folks are defining " induction, " right? Linus2nd

 

[hicetnunc]

Very interesting. So " induction " and " a posteriori " reasoning are the same for Thomas. Is that correct? But because of Hume or at least the Enlightenment the meaning of " induction " has changed, is that correct? So in discussions we should ask what exactly how folks are defining " induction, " right? Linus2nd

Yes, that’s spot on Linus. Inductive reasoning has a very different meaning for Hume than for St Thomas. And so you are right: we need to be clear on these distinct meanings when trying to compare what is essentially two different approaches to reason and knowledge. There is a methodical difference in St Thomas between a posteriori and induction, but not the kind of difference found in Enlightenment epistemology. MacIntyre for one has a lot to say on this.

 

[Blue_Horizon]

hicetnunc:

Originally Posted by Blue Horizon
*"The problem area is where you opine: “demonstrative reasoning moving … from the effect to the cause (aposteriori).” “A priori and a posteriori knowledge are thus not two distinct kinds of knowledge, but simply two methods of demonstration…Both can yield certain conclusions.” *

This is not me “opining”. You asked about what St Thomas teaches, and this is what he holds in respect to the relationship between a priori and a posteriori knowledge. The fact that Enlightenment philosophers rejected this framework is well-documented and much-discussed by philosophers (see for example, A. MacIntyre’s, Three Rival Versions of Moral Inquiry, and J. Knasas, Being & Some 20th Century Thomists). This is the fundamental difference between the Scholastic and Enlightenment understanding of a posteriori and a priori reasoning.

H&N Thanks for the references. It seems my original question boils down to what is discussed in those books. Hopefully someone may be able to provide a quick precis of the debate.
Apologies for the opining bit. As “a priori and a posteriori knowledge are thus not two distinct kinds of knowledge…” were your own words I considered them a personal inference from less explicit statements of Aquinas at ST 1a q2, a2.

I do not believe ST 1a q2 a2 (by itself) will hold the inference you seemed to make in the context of this discussion (that the nature of a cause can be known by aposteriori demonstration with the same certainty as that offered as a starting point in an apriori demonstration):

“…from the effect we proceed to the knowledge of the cause* **.
And from every effect the existence of its proper cause can be demonstrated, so long as its effects are better known to us; because since every effect depends upon its cause, if the effect exists, the cause must pre-exist.”

When we go from effects and posit a cause then, yes I agree, Aquinas says we have certain knowledge that a cause actually exists*. Aquinas does not say we have certain knowledge into the nature/essence of that cause. Yes, more and more observation of effects may give us an insight into the likely characteristics of the cause (modern meaning of induction), but it is not certain, only probable. Here Aquinas appears to remain silent on that matter.

So I believe I am forced to disagree with you if you are using this text to say that aposteriori demonstration gives certain knowledge of the essence of a cause equal to that essence already known as a starting point in apriori demonstrations.
The only common certainty between these two methods of demonstration seems to be the existence of the cause - not it essence/nature.

So I see Aquinas actually in harmony with Enlightment understanding of “induction”, he does not seem to be contradicting it.

However, you may well be right because I am only looking at this one quote from Aquinas that you gave me. Are you able to provide another where Aquinas clearly states that aposteriori demonstrations provide certain knowledge of not only the existence of a cause but also its nature (comparable to the nature of a “cause” as may be used in an apriori demonstration)?