I am perfectly persuaded that the tempers had better be unlike: I mean unlike in the flow of the spirits, in the manners, in the inclination for much or little company, in the propensity to talk or to be silent, to be grave or to be gay.
There are no more uses of "propensity" in the book.
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…now, and he knew she had a sense of humor, and she knew he did, too, and somehow he made her feel safe, made her trust that he would never bring it up again, that this terrible thing she said would remain betWeen them, that they both understood mistakes are made by all and that they should, if everyone is acknowledging our common humanity, our common frailty and propensity for sounding and looking ridiculous a thousand times a day, that these mistakes should be allowed to be forgotten.
Dave Eggers -- The Circle
I was too nervous to bother explaining that one of my father’s vices had been his propensity for dirty limericks.