The purpose of contemplation is to bring to mind the object of placement meditation. We do this by considering various lines of reasoning, contemplating analogies, and reflecting on the spiritual instructions we have heard in our classes or read.
By contemplating such instructions deeply, eventually we reach a definite conclusion or cause a specific virtuous state of mind to arise. This is the object of placement meditation.
It is helpful to memorize the contemplations given in The New Meditation Handbook so we can meditate without having to look at the text.
The contemplations given in that book are intended only as guidelines. We should supplement and enrich them with whatever reasons and examples we find helpful.