Thanks all for your comments so far.
hatsoff,
I hesitate to repeat this point, because I doubt it is necessary to discuss the argument, but I feel like I must remind you that modus ponens is not literally a “form] of thought,” but rather a logical inference.
Ok, but what is a logical inference, if not a process/form of thought?
At best you could say that modus ponens models some thinking, but even then you’d be making some steep assumptions with which I for one am not at all comfortable.
I would say that
modus ponensIf I’ve understood you correctly (which is not at all certain), then I don’t see how that’s any different from human brains. No matter how unlikely it appears, there’s always the chance that we’re wrong even about something as seemingly straightforward as, say, modus ponens, to extend your analogy. But of course we can still know with as much or nearly as much confidence that a machine operates in a particular way as we can that one’s own mind operates in another particular way.
Is there really a chance that we can be wrong with a formal argument such as
modus ponens? Sure, we can substitute incorrect values/states into p and q, but can the form of the argument ever be wrong? I don’t see how it can. Let me try to illustrate. Let p be “I turn a tap on” and q “water comes out”, so via modus ponens:
If I turn a tap on, then water comes out
I turn a tap on
therefore water comes out
Now, of course, it may not be necessary that whenever I turn a tap on water comes out, therefore the argument may fail in certain circumstances,
however the
form of the argument is truth preserving. If I turned a tap on and water didn’t come out, I wouldn’t doubt the form of the argument, the form is always vaild, rather I would doubt the first premise. Let me try another example, this time with inductive uncertainty removed: p is “Fred is not married” and q is “Fred is a bachelor”
If Fred is not married, then Fred is a bachelor
Fred is not married
Therefore Fred is a bachelor
I would ask you how we could ever be wrong about this? Where could any un-certainty in indeterminate-ness come into this? When we use this form of reasoning, it is definite, there is no ambiguity with regards to the functional form. If you were to say that we are actually indeterminate with regards to the form of this thought process, you would have to be determinate with that thought process in which you issue your denial.
Contrast this with a machine which performs
modus ponens. Say this machine consistently spits out a red chip whenever a blue chip is inserted into it. We can never be definite about the truth-preserved-ness of whatever function the machine is performing. One day it may start spitting out blue chips when blue chips are inserted, or blue chips when a red chip followed by a blue chip is inserted, or blue chips when red chips are inserted at a rate of 60 per minute etc. This indeterminism/indefinite-ness is in stark contrast to what we are doing when we think in the form of
modus ponens.
I still don’t know what “inherently indeterminate between mutually exclusive functions” is supposed to mean.
Notice all the functions that I listed above:
if Vb > y, Vout > 0V, else Vout=0V
if Vb > y, Vout > 0V, else Vout=0V only if t<1e6 hours after the transistor is created, otherwise Vout < 0V
if Vb > y, Vout >0V, else Vout=0V only if t<1e7 hours after the transistor is created, otherwise Vout = 10V
etc.
These functions cannot all be the case, i.e. only one of them can, therefore they are mutually exclusive. However, we cannot differentiate between them by simply looking at the (name removed by moderator)uts and outputs of the process, as the (name removed by moderator)uts and outputs give equal support for any of these functions (at least, if we are examining the transistor within 1e6 hours after its creation). That is what is meant by indeterminate. Hope that clears things up.
Are you just saying that it’s possible we’re making a mistake in our conception of a calculator’s mechanics?
No. What I am saying is that it is never possible to know which function is actual within the machine, for a finite number of observed (name removed by moderator)uts and outputs.