The theory presented here represents a radical departure from current treatments of the theory of knowledge. It makes the point that all such work is based on the false assumption that what makes knowledge possible is in itself knowable in some way, whereas in fact it is below the threshold of any cognitive consciousness. It is therefore necessary to seek the basis of the possibility of knowledge on entirely different levels, and in entirely novel ways. To Know or Not to Know is the first presentation of the theory in full, earlier writings being only preliminary and brief. It is aimed at the general philosopher, and the specialist in the field of epistemology, but relevant to anyone who would understand how it is possible to know anything at all.