Atheism is irrational.

[Angrboda]

Atheism cannot deny God by the intellect. For, whatever we can deny by the use of our intellect, must be defined, just as we deny circle things as square, for the definition of circle is different from the definition of square. But, God can't be define, because if He has definition, He can't be God, because by demonstration of His existence through His effects, He is necessarily Boundless. Hence, God can't be denied by the intellect.

This sounds like Berry's paradox.

Consider the expression:

       "The smallest positive integer not definable in under sixty letters."

Since there are only twenty-six letters, there are finitely many phrases of under sixty letters, and hence finitely many positive integers that are defined by phrases of under sixty letters. Since there are infinitely many positive integers, this means that there are positive integers that cannot be defined by phrases of under sixty letters. If there are positive integers that satisfy a given property, then there is a smallest positive integer that satisfies that property; therefore, there is a smallest positive integer satisfying the property "not definable in under sixty letters". This is the integer to which the above expression refers. The above expression is only fifty-seven letters long, therefore it is definable in under sixty letters, and is not the smallest positive integer not definable in under sixty letters, and is not defined by this expression. This is a paradox: there must be an integer defined by this expression, but since the expression is self-contradictory (any integer it defines is definable in under sixty letters), there cannot be any integer defined by it.

https://en.wikipedia.org/wiki/Berry_paradox