P44: It is of the nature of Reason to regard things as necessary, not as contingent.

Dem.: It is of the nature of reason to perceive things truly (by P41), viz. (by IA6) as they are in themselves, i.e. (by IP29), not as contingent but as necessary, q.e.d.

Cor. 1: From this it follows that it depends only on the imagination that we regard things as contingent, both in respect to the past and in respect to the future.

Schol.: I shall explain briefly how this happens. We have shown above (by P17 and P17 C) that even though things do not exist, the Mind still imagines them always as present to itself, unless causes occur which exclude their present existence. Next, we have shown (P18) that if the human Body has once been affected by two external bodies at the same time, then afterwards, when the Mind imagines one of them, it will immediately recollect the other also, i.e., it will regard both as present to itself unless causes occur which exclude their present existence. Moreover, no one doubts but what we also imagine time, viz. from the fact that we imagine some bodies to move more slowly, or more quickly, or with the same speed.

Let us suppose, then, a child, who saw Peter for the first time yesterday, in the morning, but saw Paul at noon, and Simon in the evening, and today again saw Peter in the morning. It is clear from P18 that as soon as he sees the morning light, he will immediately imagine the sun taking the same course through the sky as he saw on the preceding day, or he will imagine the whole day, and Peter to gether with the morning, Paul with noon, and Simon with the evening. That is, he will imagine the existence of Paul and of Simon with a relation to future time. On the other hand, if he sees Simon in the evening, he will relate Paul and Peter to the time past, by imagining them together with past time. And he will do this more uniformly, the more often he has seen them in this same order.

But if it should happen at some time that on some other evening he sees James instead of Simon, then on the following morning he will imagine now Simon, now James, together with the evening time, but not both at once. For it is supposed that he has seen one or the other of them in the evening, but not both at once. His imagination, therefore, will vacillate and he will imagine now this one, now that one, with the future evening time, i.e., he will regard neither of them as certainly future, but both of them as contingently future.

And this vacillation of the imagination will be the same if the imagination is of things we regard in the same way with relation to past time or to present time. Consequently we shall imagine things as contingent in relation to present time as well as to past and future time.

Cor 2: It is of the nature of Reason to perceive things under a certain species of eternity.

Dem.: It is of the nature of Reason to regard things as necessary and not as contingent (by P44). And it perceives this necessity of things truly (by P41), i.e. (by IA6), as it is in itself. But (by IP16) this necessity of things is the very necessity of God/Nature’s eternal nature. Therefore, it is of the nature of Reason to regard things under this species of eternity.

Add to this that the foundations of Reason are notions (by P38) which explain those things that are common to all, and which (by P37) do not explain the essence of any singular thing. On that account, they must be conceived without any relation to time, but under a certain species of eternity, q.e.d.