I think the phrase you want is ' on principle'.
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Mister MicawberI think the phrase you want is 'on principle'.I believe not. I know there are "in principle" and "on principle" and also maybe "as a matter of principle". "On principle" seems to be a basic rule or convention, however I'm talking about specific principles, as in "in principle", however with the emphasis on excluding a different possibility "by"
Anonymous I'm curious about the possbility of ever using "by principle".No, I don't think so.