[The Third Argument]

One may say:

The nature of contingency does not in itself necessitate existence, whether contingent beings are assumed to be finite or infinite in number; for anything that did so would not be contingent.

Thus, a contingent being, insofar as it is contingent, must depend upon an existent being that is not contingent. In these passages, “contingent” means possible in the restricted sense: that which admits both existence and nonexistence, with the necessary and the impossible constituting the other two categories.

But if “possible” is intended in the broad sense, as the counterpart of the impossible, then every existent being is possible in this broad sense.

An existent being exists either through itself or through something else. Not every existent being exists through itself, for existing things include those that have come into existence, and reason knows with self-evident certainty that these do not exist through themselves.

It is thus established that some existing things exist through themselves, while others exist through something else.

[The Fourth Argument]

One may say: existing things do not all exist through something other than themselves. For if that other were nonexistent, it would be impossible for an existent being to exist through what does not exist. If that other were existent, it would be an existent being outside the totality of existing things.

Since existing things do not all exist through something other than themselves, either all of them—or each individually—exist through themselves, or this is not the case. The first alternative is impossible, because things that are observed coming into existence are known with self-evident certainty not to exist through themselves. Since they neither all exist through something other than themselves nor all exist through themselves, it follows necessarily that among them are