Proposition LXII. In so far as the mind conceives a thing under the dictates of reason, it is affected equally, whether the idea be of a thing future, past, or present.
Whatsoever the mind conceives under the guidance of reason, it conceives under the form of eternity or necessity, and is therefore affected with the same certitude. Wherefore, whether the thing be present, past, or future, the mind conceives it under the same necessity and is affected with the same certitude.
Note.—If we could possess an adequate knowledge of the duration of things, and could determine by reason their periods of existence, we should contemplate things future with the same emotion as things present; and the mind would desire as though it were present the good which it conceived as future.
Consequently it would necessarily neglect a lesser good in the present for the sake of a greater good in the future. However, we can have but a very inadequate knowledge of the duration of things; and the periods of their existence we can only determine by imagination, which is not so powerfully affected by the future as by the present. Hence such true knowledge of good and evil as we possess is merely abstract or general, and the judgment which we pass on the order of things with a view to determining what is good or bad for us in the present, is rather imaginary than real. Therefore it is nothing wonderful, if the desire arising from such knowledge of good and evil, in so far as it looks on into the future, be more readily checked than the desire of things which are agreeable at the present time.
The rational mind is able to judge a future good just as well as a present one and will be able then to reject the present lesser good for the sake of obtaining the greater but more distant good. In other words, the intelligent choice is to forsake the chocolate cheese cake that is before you for the sake of next week's weight reading on the scale.
However, Spinoza notes, the future exists in our imagination which has a weaker effect on us than something really before us so it is understandable that we often choose the cake and forget the scale.