Plato's Sophist [17-18]

Disclosure, however, in relation to which there is ἀλήθεια, is itself a mode of Being, and indeed not of the beings which are first disclosed-those of the world-but, instead, of the beings we call human Dasein. Insofar as disclosure and knowledge have for the Greeks the goal of ἀλήθεια, the Greeks designate them as ἀληθεύειν, i.e., designate them in terms of what is achieved in them, ἀλήθεια. We do not intend to translate this word, ἀληθεύειν. It means to be disclosing, to remove the world from concealedness and coveredness. And that is a mode of Being of human Dasein.

It appears first of all in speaking, in speaking with one another, in λέγειν.

b) Ἀλήθεια and language (λόγος). Ἀλήθεια as a mode of Being of man (ζῷον λόγον ἔχον) or as a mode of life (ψυχή).

Thus ἀληθεύειν shows itself most immediately in λέγειν. Λέγειν ("to speak") is what most basically constitutes human Dasein. In speaking, Dasein expresses itself-by speaking about something, about the world. This λέγειν was for the Greeks so preponderant and such an everyday affair that they acquired their definition of man in relation to, and on the basis of, this phenomenon and thereby determined man as ζῷον λόγον ἔχον. Connected with this definition is that of man as the being which calculates, ἀριθμεῖν. Calculating does not here mean counting but to count on something, to be designing; it is only on the basis of this original sense of calculating that number developed.

Aristotle determined λόγος (which later on was called enuntiatio and judgment), in its basic function, as ἀπόφανσις, as ἀποφαίνεσθαι, as δηλοῦν. The modes in which it is carried out are κατάφασις and ἀπόφασις, affirmation and denial, which were later designated as positive and negative judgments. Even ἀπόφασις, the denial of a determination, is an uncovering which lets something be seen. For I can only deny a thing a determination insofar as I exhibit that thing. In all these modes of speaking, speech, φάναι, is a mode of the Being of life. As vocalization, speaking is not mere noise, ψόφος, but is a ψόφος σημαντικός, a noise that signifies something; it is φωνή and ἑρμηνεία: ἡ δὲ φωνή ψόφος τίς ἐστιν ἐμψύχου (De An. B, 8, 420b5ff.). "The φωνή is a noise that pertains essentially only to a living being. " Only animals can produce sounds. The ψυχή is the οὐσία ζωῆς, it constitutes the proper Being of something alive. Aristotle determines the essence of the soul ontologically in the same book of the De Anima: ἡ ψυχή ἐστιν ἐντελέχεια ἡ πρώτη σώματος φυσικοῦ δυνάμει ζωὴν ἔχοντος (B, 1, 412a27ff.). "The soul is what constitutes the proper presence of a living being, of a being which, according to possibility, is alive." In this definition, life is simultaneously defined as movement. We are used to attributing movement to the phenomenon of life. But movement is not understood here merely as motion from a place, local motion, but as any sort of movement, i.e., as μεταβολή, as the coming to presence of some alteration.