Books on Amazon
Significance / Principle of Significance / Peacocke: if we can imagine that a proof (evidence) supports a hypothesis, then that is not sufficient for to show that the hypothesis is significant - it could be that either the hypothesis or the evidence is independent of the other.
Cognitive Significance / Frege / Peacocke: identity a = b (not a = a) - ("informative").
Cognitive Significance / Peacocke: only if it is epistemically possible that a thing that as known to me as [you] and so-and-so, perhaps might not be so-and-so - i.e. the identity is informative (> Frege).
Chr. R. Peacocke
Sense and Content Oxford 1983