their constituent concepts be clear to everyone; rather, the requirement is that, once those concepts are grasped, reason should assent to the propositions with certainty. The conception of one as half of two is clear to everyone; hence the assent that follows it is more evident than in other cases. This is also why its clarity to the mind differs from that of the proposition that fifty-five and a quarter and an eighth is half of one hundred and ten and a half and a quarter, although both are self-evident. There are many comparable examples.

The meaning of “separate” and “co-located” is not immediately clear, since these terms are ambiguous, as explained earlier. Yet once their meaning is explained to rational people, they affirm with certainty that there is no “third category.” Likewise, since the meanings of the eternal and the originated, the necessary and the contingent, substance and accident, and similar terms are not clear in themselves to rational people generally, they do not affirm with certainty that whatever exists must fall within one of the two categories. Once the meaning is explained to them, however, they affirm this with certainty.

Thus, if rational people are told, “There are two self-subsisting beings, one of which is neither outside and separate from the other, nor inside it; neither distant, nor near it, nor far from it; neither above it nor below it; neither to its right nor to its left; neither in front of it nor behind it. Nor can one conceive of either pointing to the other, going to it, drawing near to it, becoming distant from it, moving towards it or away from it, turning towards it or turning away from it, veiling itself from it or revealing itself to it, appearing before its eyes or concealing itself from it”—or are presented with similar notions asserted by those who advocate negation—they know with necessary certainty that the existence of two such beings is impossible.