What is "necessitarianism"

Necessitarianism \Ne*ces`si*ta"ri*an*ism\, n. The doctrine of philosophical necessity; the doctrine that results follow by invariable sequence from causes, and esp. that the will is not free, but that human actions and choices result inevitably from motives; determinism.
--M. Arnold.

n. (context metaphysics English) (l en necessarianism)

Necessitarianism is a metaphysical principle that denies all mere possibility; there is exactly one way for the world to be.

It is the strongest member of a family of principles, including hard determinism, each of which deny libertarian free will, reasoning that human actions are predetermined by external or internal antecedents. Necessitarianism is stronger than hard determinism, because even the hard determinist would grant that the causal chain constituting the world might have been different as a whole, even though each member of that series could not have been different, given its antecedent causes.

Anthony Collins was the foremost defender of Necessitarianism. His brief Inquiry Concerning Human Liberty (1715) was a key statement of the determinist standpoint.

The Century Dictionary defined it in 1889–91 as belief that the will is not free, but instead subject to external antecedent causes or natural laws of cause and effect.

• Peirce, C. S. (1892) "The Doctrine of Necessity Examined", The Monist, v. II, n. 3, pp. 321-337, The Open Court Publishing Co., Chicago, IL, April 1892, for the Hegeler Institute. Google Books Eprint. Internet Archive Eprint. Reprinted Collected Papers v. 6, paragraphs 35-65, The Essential Peirce v. 1, pp. 298-311.
• Carus, Paul (1892), "Mr. Charles S. Peirce's Onslaught on the Doctrine of Necessity" in The Monist, v. 2, n. 4, July, Paul Carus, ed., 560–582, The Open Court Publishing Co., Chicago, IL, for the Hegeler Institute. Google Books Eprint. Internet Archive Eprint.
• Peirce, C. S. (1893), "Reply to the Necessitarians", The Monist, v. III, n. 4, pp. 526-570, The Open Court Publishing Co., Chicago, IL, July 1893, for the Hegeler Institute. Google Books Eprint. Internet Archive Eprint. Reprinted Collected Papers v. 6, paragraphs 588-618.
• Carus, Paul (1893), "The Founder of Tychism, His Methods, Philosophy, and Criticisms: In Reply to Mr. Charles S. Peirce" in The Monist, v. 3, n. 4, July, Paul Carus, ed., 571–622, The Open Court Publishing Co., Chicago, IL, for the Hegeler Institute. Google Books Eprint. Internet Archive Eprint. Carus's reply to Peirce's "Reply to the Necessitarians" in the same issue.