Part of PopperianEpistemology
But this doesn't imply a rejection of reason itself. Instead Popper invents an alternative, Critical Rationalism, to describe this justification free rationality.
According to this definition, someone's rationality lies not in the formation of their beliefs, but in the way that they treat them after formation. In having a disposition to not evaluate the truth of beliefs according to their genealogy or pedigree. But, having formed a belief (by the process Popper calls conjecture), a rational person is obliged to never hold it beyond further criticism. Criticism of beliefs is in terms of cross-reference against other beliefs. It would be irrational to believe two inconsistent things.
Although we have no obligation to reject beliefs because of their origin, if we are sceptical about an idea received from one source, we should cross-check it against information received from an alternative channel. This Popper suggests is what we in fact do. In contrast to the implication of justificationism, which is that we attempt to validate particular channels.
Next : ConjectureIsBlind
Doesn't this mean ICanBelieveAnythingIWant?
I heard Popper was a realist, isn't this a Coherance Theory? No, under critical rationalism, the hallmark of rationality is consistency, or better understood, the disposition to try to ensure consistency. Howver Popperianism is not a Coherence but a Correspondance Theory of Truth
One might be tempted to ask IsPopperNaturalist?
See also a TelescopeExampleOfCriticalMethod
Worth distinguishing from NaiveNegativeCriticism