I presented the cosmological proof based on causality in motion to an agnostic, who answered that this is invalid, on the basis that such causality has been disproved in the realm of quantum physics . . .
I think not. Quantum physics studies “motion” on a more specific level, seeking to understand the mechanisms it has derived from postulating and testing what happens, and how. St. Thomas (Aristotle and others) studied motion from a more general perspective.
Both “sciences” are valid ways to look at the subject, and, neither disputes the other, in my opinion. Quantum physics studies, for example, the “track” of an object in motion by understanding what happens at each point on that track, and what forces are present, as the object moves.
Thomist’s study our example object without using a microscopic lens, but rather, using a lens that sees the whole motion on a general level. So, by this method, motion is broken down into two essential parts:
potency and
act. At the beginning of any motion, an object is in
potency to be at its final destination, or
act. Also, at any place along the motion-track, the object is still in “potential” to be at its destination, or “act”. This proof postulates a “law” that says that nothing “moves” except by being “moved” by something that already exists.
Neither physics nor a general science refutes the other, nor is either intended to be a refutation of the other. The relationship is kind of like the relationship between astronomy and particle physics.
There is a concept that a particle “exists” that comes into existence and goes out of existence, in fractions of a second. These particles are said to hold electrons in their respective shells. However, their existences have not been proven and a number of scientists aren’t completely behind the postulate. They are posited, similarly to how electrons are posited, because certain “seen” behaviors seem to require them. However, even if they were to be found to exist, they may simply be unmaterialized “forces” that behave as though they were material. Besides, these particles may be “borrowed” energy/matter so they would not violate any Law of Thermodynamics.
Does this fact have a bearing on the second or third proofs of St Thomas, which I do not quite understand?
St. Thomas’s second proof is proof from
efficient causality. It postulates a “law” that nothing can be the (efficient) cause of itself, otherwise, it would be prior to itself. So, I do not believe there is any conflict here either.
According to Fr Copleston, the third proof is considered the fundamental one by neo-Thomists, but I do not quite understand what St Thomas meant by saying that we “find in nature things that are possible to be and not to be, since they are found to be generated, and to corrupt, and consequently, they are possible to be and not to be”, since he surely did not mean that there was constant ex nihilo creation of matter and, afterwards, annihiliation thereof; and as Lavoisier said: “Nothing is lost, nothing is created, everything is transformed.” Could someone please explain that proof to me, or direct me to a good explanation thereof?
The third proof is the proof from
necessity. It says that there are things in nature that come into existence and go out of existence, however, not in an
ex nihilo sense. It postulates a “law” that says that if everything can not exist then nothing would be existing now, because things that do not exist only come into existence by things that already exist. Thus, if all things are simply
possible, there must be some existing thing that is not just
possible, it must also be
necessary (necessarily existing).
For example, everything that we see has been brought into existence by something already in existence. A child is brought into existence by his/her parents. A house is brought into existence by the builders. It is possible for both of these to not exist, and, in fact, they did not prior to conception or construction. But, the same is true of everything. (This may be called “contingent” existence.) However, this being obviously true, there would have been a point, moment, or time when nothing existed, in which case we would not be here now. So, there must be some
necessary being that is not merely
possible being, but is
necessary being or else all else would not exist, and this being is God.
Merry Christmas and God bless,
JD