(philosophy) Proceeding by inquiry or investigation.
1865, Samuel Birley Rowbotham, Zetetic Astronomy, 2022 facsimile reprint, Salzwasser Verlag, page 6,
Hence, in every zetetic process, the conclusion arrived at is essentially a quotient, which, if the details be correct, must, of necessity, be true beyond the reach or power of contradiction.
Of or pertaining to zetetic astronomy (which employs zetetic principles to argue that the earth is flat).
1887, Marcellus John Thompson, "Evolution of Sound" Evolved: A Review..., Standard Publishing Company, page xix,
But another craze, much similar to Dr. Hall's philosophy, is now running its course among us, namely the Zetetic Philosophy, or the theory that the earth is flat—advocated especially by John Hampden, of England, and William Carpenter, of the United States. These people believe, with Parson Jasper, that "the sun do move."