Opposition

An opposition is the aspect of one hundred and eighty degrees: two bodies stand directly across the chart from each other, at the diameter of the circle. It is one of the five classical aspects, and unlike the conjunction it was never in doubt as a genuine aspect in Ptolemy's own terms, since two bodies at opposite points of the circle satisfy his requirement that aspecting bodies be able to behold one another; indeed the opposition is the aspect in which that mutual regard is most complete, each body looking straight across at the other along a single line. The doctrine is bound up with the same logic that gives the sextile, square and trine their standing: only configurations in which the intervening arc allows an unbroken line of sight between the two positions counted, on Ptolemy's reasoning, as aspects proper, and the conjunction was excluded on the opposite ground, that its two bodies were too close to be seen as separate at all.

The opposition's strength in judgment, matched among the five perhaps only by the trine and the conjunction it excluded from the strict class, has kept it central to aspect doctrine ever since. The full moon, which is technically an opposition of the lights, and the new moon, technically a conjunction of them, are the most familiar everyday instances of the two relations, and the pairing of the two in ordinary speech about the sky likely did as much as any technical text to keep the opposition's meaning, confrontation met by full visibility, alive outside specialist circles.