But at this point, perhaps, a glimmer of hope dawns upon us. We ask the reason for these Ideas. Has not Plato asserted that the ultimate reason and ground of all the lower Ideas will be found in the supreme Idea of {244} the Good? Now if this is so, it means that the lower Ideas must find their necessity in the highest Idea. If we could see that the Idea of the Good necessarily involves the other Ideas, then these other Ideas would be really explained. In other words, we ought to be able to deduce all the other Ideas from this one Idea. It ought to be possible to show that, granted the Idea of the Good, all the other Ideas necessarily follow, that to assume the Good and deny the other Ideas would be self-contradictory and unthinkable. There are examples in Plato of the kind of deduction we require. For example, in the "Parmenides" he showed that the Idea of the one necessarily involves the Idea of the many, and vice versa. You cannot think the one without also thinking the many. This means that the many is deduced from the one, and the one from the many. Just in the same way, we ought to be able to deduce the Idea of whiteness from the Idea of the Good. But this is clearly not possible. You may analyse the Good as long as you like, you may turn it in every conceivable direction, but you cannot get whiteness out of it. The two Ideas do not involve each other. They are thinkable apart. It is quite possible to think the Good without thinking whiteness. And it is the same with all the other Ideas. None of them can be deduced from the Good.