Is it necessary for one who longs for liberation to inquire into the nature of categories (tattvas)?

Just as one who wants to throw away garbage has no need to analyse it and see what it is, so one who wants to know the Self has no need to count the number of categories or inquire into their characteristics; what he has to do is to reject altogether the categories that hide the Self. The world should be considered like a dream.

Is there no difference between waking and dream?