§19.1Fr. 19
Θ. ἐν τῷ πρώτῳ τῶν ἑαυτοῦ Φυσικῶν καὶ καθʼ ἕκαστον γένος τῶν κατηγοριῶν τὴν κίνησιν θεωρεῖσθαί φησι γράφων οὕτως· περὶ δὲ κινήσεως τὸν μὲν καθόλου καὶ κοινὸν λόγον οὐ χαλεπὸν ἀποδοῦναι καὶ εἰπεῖν, ὡς ἐνέργειά τίς ἐστιν ἀτελὴς τοῦ δυνάμει ὄντος ᾗ τοιοῦτον καθʼ ἕκαστον γένος τῶν κατηγοριῶν διὸ καὶ προελθὼν ὀλίγον ὁ Θ. ζητεῖν δεῖν φησὶ περὶ τῶν κνήσεων, εἰ αἱ μὲν κινήσεις εἰσὶν αἱ δὲ ὥσπερ ἐνέργειαί τινες.
Fr. 19 Theophrastus says in the first book of his Physics that motion is also observed in each genus of the categories, writing as follows: "On the one hand, regarding motion, it is not difficult to render and state the universal and common definition, namely that it is a certain incomplete activity of that which exists potentially, insofar as it is such, in each genus of the categories." Therefore, also proceeding a little further, Theophrastus says that one must investigate regarding motions, whether some are motions and others are as it were certain activities.