Rereading a book of Roger Scruton’s — called simply Conservatism: An Invitation to the Great Tradition — I came across this definition which is both sturdy but also shows its own date:

Modern conservatism began as a defence of tradition against the calls for popular sovereignty; it became an appeal on behalf of religion and high culture against the materialist doctrine of progress, before joining forces with the classical liberals in the fight against socialism. In its most recent attempt to define itself it has become the champion of Western civilisation against its enemies, and against two of those........

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