There are at least two quite different concepts of truth: formal and factual. Leibniz called them vérités de raison and vérités de fait respectively. Whereas the formal truths are those of logic and mathematics, the factual truths are characteristic of ordinary knowledge, science, and technology. For example, while "There are infinitely many prime numbers' is a formal truth, "There are about six billion people at this time" is a factual truth. The confusion between the two kinds of truth is even worse than the confusion between value and price.