In the observable world causes are found to be ordered in series; we never observe, nor ever could, something causing itself, for this would mean it preceded itself, and this is not possible. Such a series of causes must however stop somewhere; for in it an earlier member causes an intermediate and the intermediate a last (whether the intermediate be one or many). Now if you eliminate a cause you also eliminate its effects, so that you cannot have a last cause, nor an intermediate one, unless you have a first. Given therefore no stop in the series of causes, and hence no first cause, there would be no intermediate causes either, and no last effect, and this would be an open mistake. One is therefore forced to suppose some first cause, to which everyone gives the name 'God.'
Thomas Aquinas, 1224-1274, Summa Theologia, (from Readings in Medieval History, Patrick Geary, University of Toronto Press, 2010, p. 481).
Is this a good argument? What are the possible objections? Can anything be said in answer to them.?
A Diary of Private Prayer
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