Whenever it is determined in anywise from within, it regards things clearly and distinctly, as I will show below.
PROP.XXX.

We can only have a very inadequate knowledge of the duration of our body.
Proof .-- The duration of our body does not depend on its essence (II.Ax.

i.), nor on the absolute nature of God (I.
xxi.).

But (I.xxviii.) it is conditioned to exist and operate by causes, which in their turn are conditioned to exist and operate in a fixed and definite relation by other causes, these last again being conditioned by others, and so on to infinity.
The duration of our body therefore depends on the common order of nature, or the constitution of things.

Now, however a thing may be constituted, the adequate knowledge of that thing is in God, in so far as he has the ideas of all things, and not in so far as he has the idea of the human body only.