Book 4
24
I mean, e.g., that white is cultured and cultured white merely because both are accidents of a man. But it is not in this sense—that both terms are accidents of something else—that Socrates is cultured. Therefore since some accidents are predicated in the latter and some in the former sense, such as are predicated in the way that white is of Socrates cannot be an infinite series in the upper direction; e.g. there cannot be another accident of white Socrates, for the sum of these predications does not make a single statement.
25
Nor can white have a further accident, such as cultured; for the former is no more an accident of the latter than vice versa; and besides we have distinguished that although some predicates are accidental in this sense, others are accidental in the sense that cultured is to Socrates; and whereas in the former case the accident is an accident of an accident, it is not so in the latter; and thus not all predications will be of accidents.
26
Therefore even so there will be something which denotes substance. And if this is so, we have proved that contradictory statements cannot be predicated at the same time.
26
Again, if all contradictory predications of the same subject at the same time are true, clearly all things will be one.
27
For if it is equally possible either to affirm or deny anything of anything, the same thing will be a trireme and a wall and a man; which is what necessarily follows for those who hold the theory of Protagoras.i.e., that all appearances and opinions are true. For if anyone thinks that a man is not a trireme, he is clearly not a trireme; and so he also is a trireme if the contradictory statement is true.
