Contrariety (Latin: contrarietas)
Definition
Contrariety is a three-planet horary configuration in which a retrograde planet wrecks a conjunction that two other planets were forming. A swift planet stands at the highest degrees of a sign; a slower, more ponderous planet sits at fewer degrees; and a third planet, swifter still but at the lowest degrees, applies toward the ponderous one. Before that third planet can arrive, the first turns retrograde, back-tracks into conjunction with the ponderous planet ahead of the seeker, then releases it and joins the third planet instead — destroying the conjunction the seeker was making.
In Tradition
In medieval Latin horary, drawn from the Arabic tradition, contrariety is one of the ways a matter is denied. The interfering planet acts contrary to its natural order — heavier planets should be met by lighter ones moving forward, not joined by a heavier planet doubling back in retrogradation. Bonatti treats it as distinct from refranation and frustration: it needs three planets and a retrograde swap, in which the back-tracking planet steals the receiver's conjunction and then cuts off the seeker.
In Practice
You identify the three planets by speed and degree: a swift planet high in a sign, a more ponderous planet at fewer degrees, and a third swifter planet lower still applying to the ponderous one. Check whether the highest planet is about to station and turn retrograde. If it does, trace its retrograde path: it back-tracks into conjunction with the ponderous planet before the original seeker arrives, then continues retrograde to join the seeker itself. When this happens, judge the matter destroyed — the conjunction the seeker was forming never completes. Bonatti's worked case puts Jupiter at Aquarius 26, Saturn at 24, and Mars at 15 seeking Saturn; Jupiter goes retrograde, joins Saturn, passes him, and joins Mars, so Mars never reaches Saturn. Because the doctrine requires you to track retrograde cycles and per-planet speeds for all three bodies, read it alongside refranation, frustration, and prohibition, and weigh any reception before passing final judgment.
Historical Origin
The doctrine is set out in Guido Bonatti's Liber Astronomiae (c. 1277, Vol XI Part III, the chapter 'Concerning the Contrariety of the Planets'), preserved in Robert Hand's Project Hindsight translation. Bonatti's Liber is the principal Latin conduit for the Arabic horary tradition of Sahl ibn Bishr and Masha'allah, within whose modes of denial this configuration belongs.