Cruʹcial

A crucial test. A very severe and undeniable one. The allusion is to a fancy of Lord Bacon’s, who said that two different diseases or sciences might run parallel for a time, but would ultimately cross each other: thus, the plague might for a time resemble other diseases, but when the bubo or boil appeared, the plague would assume its specific character. Hence the phrases instanʹtia crucis (a crucial or unmistakable symptom), a crucial experiment, a crucial example, a crucial question, etc.

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