Abstract
About the argument of the συμπλοκη των ειδων in the Sophist 251-259 most attention has been paid to the question how many meaning(or usages)of the verb ειναι Plato here distinguishes. But the argument cannot, I think, be discussed apart from the whole structure of Plato's theory of Forms. I try to show that the argument gives the ontological ground for the theory of Forms. In the examination of the communion of the five μεγστα γενη(255E-256D), three γενη are ascertained as Forms which all the others partake in. The ontological functions of these three Forms are: το ον makes a Form to be(to exist) ; ταυτον makes a Form the same as itself; θατερον makes a Form different from the others. In the so-called vowel-analogy (253A-C) , on the other hand, Plato distinguishes two kinds of all-pervasive Forms. I submit it is most reasonable to interpret το ον as the vowel Form, and ταυτον and θατερον as the Forms responsible for the διαιρεσι&b.sigmav;. The function of το ον for the communion of Forms has no direct relation to the type of the statement 'A is B'. το ον just certifies ontologically that Form A is, which means, for Form A itself, that Form 'A is A. That which certifies the 'is' of 'Form A is' is το ον, while the 'is' of 'Form A is A' comes from the essential nature of Form A. The meaning of the 'is' in the two statements 'Form A is' and 'Form A is A' is, accordingly, ontologically different. In this way, i.e. through this function of το ον, the argument offers the ontological ground for the existence of Forms, which has been a hypothesis since the Phaedo. When Form A is, by participating in το ον, and is A, because of its own nature, it has thus itself the power to participate in others. The relation of participation and non-participation between Form A and Form B is decided according to their essential nature. The function of ταυτον and that of θατερον are co-supplementary. They guarantee ontologically that Form A is relationally(προ&b.sigmav; τι)A itself, το ον, ταυτον and θατερον all guarantee the same fact that Form A is A. But το ον guarantees that Form A is in itself(καθ' αυτο)A, while ταυτον and θατερον, that Form A is προ&b.sigmav; τι A itself. This fact has a great significance in the relation of participation among Forms. When Form A is B by participating in Form B, the relation does not entail the disappearance of the fact that Form A is the same as itself and different from Form B, namely that Form A is A. There can be no relation of participation between Form A and Form B when this consequence takes place. The function of ταυτον and θατερον in the relation of participation among Forms may be justly called the cause of the διαιρεσι&b.sigmav;, when seen in the genus-species relations which construct the realm of the Forms. Here we can understand the internal connection of the two descriptions of the task of the dialectic which Plato just in this argument gives(253B11-C 1, C 1-3).
