Aquinas' First Way

Aquinas' First Way is often referred to as %%'motion' or 'change'%%. Aquinas stated that %%when we observe the universe, we notice that things tend to be in a state of change or motion.%% From this observation, Aquinas noted that things do not do this of their own accord but are instead 'moved' (or changed) by something else (in this, Aquinas is restating what Aristotle had previously said).

'It is certain, and evident to our senses, that %%in the world some things are in motion.%% Now whatever is in motion is put in motion by another, for nothing can be in motion except it is in potentiality to that towards which it is in motion; whereas a thing moves inasmuch as it is in act. %%For motion is nothing else that the reduction of something from potentiality to actuality%%. But nothing can be reduced from potentiality to actuality, except by something in a state of actuality.' (Aquinas, Summa Theologica)

Aquinas stated that if we looked back down this sequence of movements/changes, we would have to eventually come to %%something that started the whole sequence off%%. Now, as all things in the universe (that are observable) are either moving or movers, we need to find a point that started these -and that means, necessarily, looking outside the universe -i.e. to something which has not been moved by anything else and is in fact incapable of being moved/changed by anything else but is responsible for initiating the whole sequence of movement/change.

Aristotle named this the %%Prime Mover%%, and Aquinas developed this into the %%'Unmoved Mover'%% -'that which all men call God. '

To illustrate this further, Aquinas builds on Aristotle's example and explanations. %%Aristotle speaks of things moving from a state of 'potentiality (the ability to be able to become something else) towards a state of 'actuality' (when something is in its fully realised state).%%

However, both Aristotle and Aquinas noted that this change could only happen if something that already possessed a state of actuality acted on that which was in its state of potentiality. This third party is known as the 'efficient cause.'

%%Aristotle used the example of a block of marble (potential) becoming a statue (actual) but only when acted upon by the sculptor (efficient cause).%%

%%Aquinas uses the example of wood becoming hot%% in order to illustrate this point:

'Thus that which is actually hot, as fire, makes wood, which is potentially hot, to be actually hot, and thereby moves and changes it. Now it is not possible that the same thing should be at once in actuality and potentiality in the same respect, but only in different respects. %%For what is actually hot cannot simultaneously be potentially hot; but it is simultaneously potentially cold%%. It is therefore impossible that in the same respect and in the same way a thing should be both mover and moved i.e. that is should move itself. (Aquinas)

In this, %%Aquinas is stating that the fire that makes the wood hot must already have the property of hotness within itself in order, in turn, to make the wood hot%%. Were it to have any other state (e.g. coldness) within itself then it would be impossible to make the wood hot.

Summary

  1. Whenever something undergoes change it is caused to do so by something.
  2. Nothing can be the cause of it’s own change.
  3. Whenever something changes it is caused to do so by something other than itself.
  4. The chain connecting things which change and things which initiate the changes cannot be infinite.