The Only Use of

surmise
in
The Phantom Tollbooth

It's local ordinance 17.5:3894" Milo quickly pulled the rule book from his pocket, opened to the page, and read, "Ordinance 1753894 It shall be unlawful, illegal, and unethical to think, think of thinking, surmise, presume, reason, meditate, or speculate while in the Doldrums.†
p. 24.9

Definition:

to guess something is true or form an opinion based on incomplete evidence