Both Uses

theorize
in
Middlemarch
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She was thoroughly charming to him, but of course he theorized a little about his attachment.†
Chpt 1 *
Perhaps that was a more cheerful time for observers and theorizers than the present; we are apt to think it the finest era of the world when America was beginning to be discovered, when a bold sailor, even if he were wrecked, might alight on a new kingdom; and about 1829 the dark territories of Pathology were a fine America for a spirited young adventurer.†
Chpt 2

Definitions:

(1) (theorize)
to form a theory (a belief about how something works or came about -- often without having absolute proof)
(2) (meaning too rare to warrant focus)