Certainty is perfect knowledge that has total security from error, or the mental state of being without doubt.Objectively defined, certainty is total continuity and validity of all foundational inquiry, to the highest degree of precision. Something is certain only if no skepticism can occur. Philosophy (at least historical Cartesian philosophy) seeks this state.[citation needed]It is widely held that certainty about the real world is a failed historical enterprise (that is, beyond deductive truths, tautology, etc.). This is in large part due to the power of David Hume's problem of induction. Physicist Carlo Rovelli adds that certainty, in real life, is useless or often damaging (the idea is that "total security from error" is impossible in practice, and a complete "lack of doubt" is undesirable).