Arguments Against Thomistic philosophy

[polymath257]

Well, for one, Aristotle thought that any movement (which he regarded as any change at all) requires a force. We now know that isn't true: motion thorugh space doesn't require a force--a *change* of direction or speed does.

Talk about straw man! Philosophy 101, my friend. The 1W has nothing to do with Newtonian physics. It’s about change.

As for contingency, a unicorn isn't something that 'possibly exists' but simply fails to do so. It is something that *doesn't* exist. There is no modifier on existence. Something either exists or not.[/i]

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…change is just that: change. It isn't a 'potential' that is 'actualized', it is simply a change… Things either exist or they do not. A non-existent thing doens't have properties like potentiality.

It is quite possibly the case that unicorns cannot possibly exist in all possible worlds. Things either exist or they don’t. Sure. But both points are irrelevant.

The distinction between act and potency is necessary to resolve the dilemma between Parmenides and Heraclitus of how things can change while preserving their being. It’s difficult to argue that things don’t have a range of potentials into which they could change. An acorn has the potential to grow into a mature tree, but no potential to become a puppy. At the same time, the acorn is the same oak as the mature tree. It’s an actual thing manifesting its potential.

And I strongly disagree here. Things have the possibility of interaction with other things, which can change either or both. Identity above the microscopic level isn't preserved, except in language (the ship of Theseus is, strictly speaking, a different ship when the first board is changed. WE are the ones that use language to say the two ships are the 'same' in some sense. I am not the same person I was yesterday if we are speaking strictly. it is only the vagaries of language that make me the same as in the past.
So, no, that acorn is NOT the same as the full grown tree. There is a causal connection, but they are not the same thing. For one thing, the tree has a much larger mass than the acorn, so they are not equal (which means all properties have to be the same). And that 'potential' of growing into a tree has, at its base, a whole environment to support it. A different environment (say with genetic engineering of the right level of technology) might well be able to make it grow into a puppy.
In particular, again, change is simply change. It isn't a pre-existing 'potential' that is 'actualized'. We don't have things bundled up with all of their potentials, some of which are actualized and others are not. We simply have things that interact with other things in certain ways.

As for 'possible worlds', well, to the extent it is a coherent notion, it is useless and to the extent it can be used, it is incoherent. The notion of 'logical consistency' is way, way, way too weak to get anywhere.