Possibility and Necessity





 The third way is taken from possibility and necessity and states that: In nature things that are possible to be and not to be, since they are found to be brought into existance (created), and to fall out of existance (to die) consequently, they are possible to be and not to be. But it is impossible for these to always exist, for that which is possible to exist at some time is not. Therefore, if everything is possible not to be, then at one time there could have been nothing in existence. If this were true, even now there would be nothing in existence, because every object is contingent, that which does not exist only begins to exist by something already existing.

 Therefore, if at one time nothing was in existence, it would have been impossible for anything to have begun to exist; and thus even now nothing would be in existence – which is absurd. Therefore, not all beings are merely possible, but there must exist something the existence of which is necessary. But every necessary thing either has its necessity caused by another, or not. Now it is impossible to go on to infinity in necessary things which have their necessity caused by another, as has been already proved in regard to efficient causes. Therefore we cannot but postulate the existence of some being having of itself its own necessity, and not receiving it from another, but rather causing in others their necessity. This all men speak of as God.

Table of Content
Aquinas' Five Ways Glossary of Terms
 * The First Way- The Unmoved Mover
 * The Second Way - The Uncaused Causer
 * The Third Way - Possibility and Necessity
 * Infinite Regress
 * Classical Thiesm