In terminology, exist (CR:1516), from Latin existere “to come into being” (Merriam) or “to step out, stand forth, emerge, appear; be” (OED), from ex- + -sistere “to stand, stop”, refers to something that has physically measureable form; is real or has reality; as opposed to something imaginary, fictional, or mythological (e.g. god, caloric, ether, life, or unicorns, etc.). [1]

The following are noted quotes:

“Believe me, dear Sir: there is not in the British Empire a man who more cordially loves a union with Great Britain than I do. But, by the God that made me, I will cease to exist before I yield to a connection on such terms as the British Parliament propose; and in this, I think I speak the sentiments of America.”
Thomas Jefferson (1775), “Letter to John Randolph”, Nov 29 [2]

See also
Existence of god
Reaction existence
Stages of existence

1. (a) Exist – Merriam-Webster Collegiate Dictionary.
(b) Exist – EtymOnline.com.
2. (a) Jefferson, Thomas. (1775). “Letter to John Randolph”, Nov 29.
(b) Jefferson, Thomas. (1853). The Writings of Thomas Jefferson: Autobiography, Correspondence, Reports, Messages, Addresses, and Other Writings, Official and Private, with Appendix, Vol One (editor: H.A. Washington). Correspondence (pgs. 202-04; quote, pg. 203). Taylor & Maury.
(c) Hazelton, John H. (1906). The Declaration of Independence: Its History (pg. 19). Da Capo Press, 1970.

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