Credulosity

But what adequate superlative shall we invent to express the credulity, the credulosity run mad, of those who, in a matter of scientific belief, deliberately accept such odds.

Source: wiktionary

[…] here the Friendly Visitor must proceed with due caution and proper consideration of the credulosity of her interviewee— take a shower bath at the club nearly every night, with out any deadly results up to date

Source: wiktionary

[…] further, since those members of the audience who perceive the lie will soon go elsewhere for their information, the “credulosity quotient” of the remaining audience tends to rise.

Source: wiktionary