M must necessarily be present with every O, but it was supposed not to be present with a certain O, and if M is present with every N, and not with every O, there will be a syllogism, that N is not present with every O, and the demonstration will be the same. But if M is predicated of every O, but not of every N, there will not be a syllogism; let the terms of presence be "animal," "substance," "crow," and of absence "animal," "white," "crow;" neither will there be a syllogism when M is predicated of no O, but of a certain N, let the terms of presence be "animal," "substance," "stone," but of absence, "animal," "substance," "science."
When therefore universal is opposed to particular, we have declared when there will, and when there will not, be a syllogism; but when the propositions are of the same quality, as both being negative or affirmative, there will not by any means be a syllogism. For first, let them be negative, and let the universal belong to the major extreme, as let M be present with no N, and not be present with a certain O, it may happen therefore that N shall be present with every and with no O; let the terms of universal absence be "black," "snow," "animal;" but we cannot take the terms of universal presence, if M is present with a certain O, and with a certain O not present. For if N is present with every O, but M with no N, M will be present with no O, but by hypothesis, it was present with some O, wherefore it is not possible thus to assume the terms. We may prove it nevertheless from the indefinite,
