“The moral is obvious. You can't trust code that you did not totally create yourself.”
Ken Thompson, Reflections on Trusting Trust (1984) · Turing Award lecture, closing section · read it
Kept because the whole supply-chain security field is a footnote to this one sentence. He proved it with a compiler that planted a back door in itself and left no trace in the source. The lesson is not paranoia; it is knowing where your trust actually bottoms out.