This method of procedure is alike applicable to demonstration in Philosophy or in any of the special sciences,[63] and to debate in Dialectic. In both, the premisses or _principia_ of syllogisms must be put together in the same manner, in order to make the syllogism valid. In both, too, the range of topics falling under examination is large and varied; each topic will have its own separate premisses or _principia_, which must be searched out and selected in the way above described. Experience alone can furnish these _principia_, in each separate branch or department. Astronomical experience--the observed facts and phenomena of astronomy--have furnished the data for the scientific and demonstrative treatment of astronomy. The like with every other branch of science or art.[64] When the facts in each branch are brought together, it will be the province of the logician or analytical philosopher to set out the demonstrations in a manner clear and fit for use. For if nothing in the way of true matter of fact has been omitted from our observation, we shall be able to discover and unfold the demonstration, on every point where demonstration is possible; and, wherever it is not possible, to make the impossibility manifest.[65] [Footnote 63: Ibid. p. 46, a. 8**: [Greek: kata\ me\n a)lê/theian e)k tô=n kat' a)lê/theian _diagegramme/nôn_ u(pa/rchein, ei)s de\ tou\s dialektikou\s sullogismou\s e)k tô=n kata\ do/xan prota/seôn.] Julius Pacius (p. 257) remarks upon the word [Greek: diagegramme/nôn] as indicating that Aristotle, while alluding to special sciences distinguishable from philosophy on one side, and from dialectic on the other, had in view geometrical demonstrations.] [Footnote 64: Analyt. Prior. I. xxx. p. 46, a. 10-20**: [Greek: ai( d' a)rchai\ tô=n sullogismô=n katho/lou me\n ei)/rêntai--i)/diai de\ kath' e(ka/stên ai( plei=stai. dio\ ta\s me\n a)rcha\s ta\s peri\ e(/kaston e)mpeiri/as e)/sti paradou=nai. le/gô d' oi(=on tê\n a)strologikê\n me\n e)mpeiri/an tê=s a)strologikê=s e)pistê/mês; lêphthe/ntôn ga\r i(kanô=s tô=n phainome/nôn ou(/tôs eu(re/thêsan ai( a)strologikai\ a)podei/xeis. o(moi/ôs de\ kai\ peri\ a)/llên o(poianou=n e)/chei te/chnên te kai\ e)pistê/mên.] What Aristotle says here--of astronomical observation and experience as furnishing the basis for astronomical science--stands in marked contrast with Plato, who rejects this basis, and puts aside, with a sort of contempt, astronomical observation (Republic, vii. pp. 530-531); treating acoustics also in a similar way. Compare Aristot. Metaphys. [Greek: L]. p. 1073, a. 6, seq., with the commentary of Bonitz, p. 506.]