More of Pythagoras' teachings.
εἶτ᾽ ἐπὶ τουτέοισιν ἀριθμέειν: "And in addition to these things (I will teach you) to count." ἐπί + dat. often means "in addition to" (and indeed this use appears again near the end of this section). τουτέοισιν is the Ionic equivalent of the Attic form τούτοις.
δοκέεις: uncontracted pres. 2 sing. act. indic. from δοκέω: think, suppose, imagine. Remember that the Attic dialect loves to contract vowels more than most other dialects. The speaker is depicted as being Ionic and so it is not surprising to see Lucian use uncontracted verb forms in his speech. Four is equated with ten here because of the Pythagorean interest in the number 10. Adding up 1, 2, 3, and 4 gives us 10. The mention of the perfect triangle presumably is related to the τετρακτύς, a triangle created with four points on the bottom row, three on the next row up, two on the following row, and one point at the top. Pythagoreans attributed mystical as well as musical significance to this figure (the adjacent rows could refer to important musical ratios).
μά: Particle used in asseverations and oaths, with acc. of the deity or thing appealed to. The word is on its own neither affirmative nor negative, but is made so by prefixing ναί or οὐ respectively. In this instance, the buyer says "not then by your greatest oath, (i.e.) by the Four," immediately appending the phrase "by the Four" to specify that greatest oath. Four was an important number for the Pythagoreans in several ways and note that the four elements appear again later in this section.
οὐ...οὔποτε: in Greek, if a negative is followed in the same clause by a compound negative (οὔποτε, οὐδείς, etc.), the second negative does not cancel the first one but confirms it (S. 2761). In this passage οὔποτε appears at the outset of the next clause and so confirms and makes more emphatic the negative οὐ in the previous clause (S. 2762).
μετά: used adverbially here to mean "later."
ξεῖνος, ου, ὁ: Ionic for ξένος, ου, ὁ.
εἴσεαι: uncontracted 2nd sing. future mid. indic. > οἶδα, εἴσομαι.
πέρι: note the accent, which indicates that the preposition follows its object (anastrophe of the bisyllabic preposition: S. 175a). This occurs in prose only with the preposition περί.
ἠέρος: Ionic for ἀέρος, gen. sg. from ἀήρ.
αὐτέοισιν: Ionic for αὐτοῖς.
ὁκοῖα: Ionic for ὁποῖα, "of what sort."
ὅκως: Ionic for ὅπως, "how."
φορή: Ionic for φορά: “motion” (of the universe and heavenly bodies).
ὁκοῖα ἐόντα μορφὴν ὅκως κινέονται: literally "and being what sorts of things with respect to their shape, how they move." The sentence has three indirect questions with a connective between the first two questions but nothing explicitly tying the third question to the list. This lack of a connective (asyndeton) is common in quick and animated conversations such as we have here (S. 2166).
καὶ μάλα: "certainly" (καὶ is here functioning to increase the force of the intensive adverb μάλα. For similar uses of the adverbial καί, see S. 2882c.
ἐμφανέα: Ionic for ἐμφανῆ > ἐμφανής, -ές clear, visible to the eye, manifest. You must supply a subject (fire, earth, air, and water as a collective) and the appropriate form of the verb ἔχειν from the previous line (a common sort of ellipse you see often in excited exchanges in Greek tragedy or in the dialogues of Plato).
οἷά τε (sc. ἐστι): "They would not be able (to move)" (with the neuter pl. οἷα representing the continuation of fire, earth, air and water as the subject).
κινέεσθαι: in the passive this verb can mean "be put in motion, go."
γνώσεαι τὸν θεὸν ἐόντα ἀριθμόν...: with verbs of knowing, showing, and perception, indirect statement is expressed with a subject accus. and an accusative participle (S. 2106 and S. 2110) . Note the Ionic forms as well: uncontracted second person γνώσεαι (Attic: γνώσει), the participle ἐόντα (Attic: ὄντα), and ἁρμονίην (Attic: ἁρμονίαν). The Attic sound change of η to (long) α after a stem ending in ε, ι, ρ is not maintained in Ionic.
