a fortiori

(Latin) with more reason, for a still stronger reason

The Latin phrase literally means one of the following:"from the stronger""even more so""with even stronger reason" It denotes a proof of a claim by means of an already proved stronger claim. Example: If it is forbidden to ride a bike with an extra passenger, then it is also forbidden to ride a bike with two extra passengers.
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Catch-22 is a satirical, historical fiction novel by the American author Joseph Heller, first published in 1961. The novel, set during the later stages of the Second World War from 1943 onwards, is frequently cited as one of the great literary works of the Twentieth century.The novel follows Yossarian, a U.S. Army Air Forces B-25 bombardier, and a number of other characters. Most events occur while the airmen of the Fighting 256th (or "two to the fighting eighth power") Squadron are based on the island of Pianosa, west of Italy. Many events in the book are repeatedly described from differing points of view, so the reader learns more about the event from each iteration. The narrative also describes events out of sequence, and furthermore the events are referred to as if the reader already knows all about them.
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Adverb
1. for a still stronger, more certain reason; "if you are wrong then, a foritori, so am I"
(synonym) with greater reason, with more reason

adv. a fortiori

adv. a fortiori, all the more, more so, even more, with stronger reason