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When did Euclidean Fifth Postulate comes to be called the Parallel Postulate? It is taken for granted. Did Euclid refer to the fifth postulate as the Parallel Postulate?

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The fifth postulate does not specifically talk about parallel lines, it is only a postulate related to parallelism. Euclid gave the definition of parallel lines in Book I, Definition 23 just before the five postulates. However, we see that there is the following equivalence:

Equivalence to the Euclidean Parallel Postulate

About the history of the fifth postulate see the article

History of the Parallel Postulate by Florence P. Lewis.

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  • $\begingroup$ But who first thought the fifth postulate addressed the problem of parallel lines? $\endgroup$ – user56930 Jan 15 '18 at 2:15
  • $\begingroup$ I think it is answered in the article about the history about the fifth postulate. $\endgroup$ – Dietrich Burde Jan 15 '18 at 9:47
  • $\begingroup$ Thanks I am going to re-read it carefully. I scanned it. It seems to me that Euclid did not call it a parallel postulate. So he shouldn't be accused of begging any questions $\endgroup$ – user56930 Jan 15 '18 at 13:19
  • $\begingroup$ Doesn't parallel lines get proven later when parallel planes get transacted by a transversal plane? $\endgroup$ – user56930 Apr 1 '19 at 19:54
  • $\begingroup$ Article ...thanks $\endgroup$ – user56930 Dec 21 '19 at 0:32

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