My wife asked, out of the blue, “What does ‘it stands to reason’ mean? When you think about it, it doesn’t make any sense.” I thought about it, and sure enough, it didn’t make any sense. So I did a little research and discovered that it’s a reminder of an obsolete phrase “to stand to,” meaning (in the OED’s words) ‘To submit oneself to, abide by (a trial, award); to obey, accede to, be bound by (another’s judgement, decision, opinion, etc.).’ So originally something “stood to (obeyed) reason” in the same way as a person “stood to a judgment”; when the verbal phrase was eroded by time, the cliché remained behind, a lone outcropping, as puzzling as one of the oddly shaped mesas of Coconino County.
Some examples of the earlier usage:
1584 LYLY Campaspe I. iii. 76 In kinges causes I will not stande to schollers arguments. 1616 A. CHAMPNEY A Treatise on the Vocation of Bishops 21 Such a Reformer is not bound to stand to the judgement of the Church. 1692 BENTLEY Boyle Lect. vi. 5 Will they not stand to the grand Verdict and Determination of the Universe? 1700 J. TYRRELL Hist. Eng. II. 889 The King summon’d [them] to appear.., and stand to the Law