by philosophers like Hegel, Peirce, and Popper. Although Peirce introduced fallibilism, he seems to preclude the possibility of us being mistaken in our mathematical beliefs. Mathematical fallibilism appears to uphold that even though a mathematical conjecture cannot be proven true, we may consider some to be good approximations or estimations of the truth. This so called verisimilitude may provide us with consistency amidst an inherent incompleteness in mathematics. Mathematical fallibilism differs from quasi-empiricism, to the extent that the latter does not incorporate inductivism, a feature considered to be of vital importance to the foundations of set theory. In the philosophy of mathematics, the central tenet of fallibilism is undecidability (which bears resemblance to the notion of isostheneia, or "equal veracity"). Two distinct types of the word "undecidable" are currently being applied. The first one relates to the continuum hypothesis; the hypothesis that a statement can neither be proved nor be refuted in a specified deductive system. The continuum hypothesis was proposed by mathematician Georg Cantor in 1873. This type of undecidability is used in the context of the independence of the continuum hypothesis, namely because this statement is said to be independent from the axioms in Zermelo–Fraenkel set theory combined with the axiom of choice (also called ZFC). Both the hypothesis and its negation are consistent with these axioms. Many noteworthy discoveries have preceded the establishment of the continuum hypothesis. In 1877, Cantor introduced the diagonal argument to prove that the cardinality of two finite sets is equal, by putting them into a one-to-one correspondence. Diagonalization reappeared in Cantors theorem, in 1891, to show that the power set of any countable set must have strictly higher cardinality. The existence of the power set was postulated in the axiom of power set; a vital part of Zermelo–Fraenkel set theory. Moreover, in 1899, Cantor's paradox was discovered. It postulates that there is no set of all cardinalities. Two years later, polymath Bertrand Russell would invalidate the existence of the universal set by pointing towards Russell's paradox, which implies that no set can contain itself as an element (or member). The universal set can be confuted by utilizing either the axiom schema of separation or the axiom of regularity. In contrast to the universal set, a power set does not contain itself. It was only after 1940 that mathematician Kurt Gödel showed, by applying inter alia the diagonal lemma, that the continuum hypothesis