It seems to me that Leibniz's definition of innate ideas is that they are ideas which, (i) the mind has the disposition to accept, and (ii) that they are derived from materials found in the understanding alone.

My question is this: does this definition not merely describe necessary truths? The mind obviously has the disposition to accept necessary truths - upon consideration, it becomes impossible to conceive of their not being true. Necessary truths are also found in the understanding alone (i.e they are known a priori).

As far as I am aware, Leibniz does not argue that the actual content of certain ideas is known innately; we are not born with the knowledge that 1 + 1 = 2. Instead, he only argues that it is our disposition to accept such truths (along with their being knowable a priori) which constitutes their innateness. Given this, it seems that there is no difference between his definition of innatism and the definition of necessary truths. Thus, does it not become superfluous to even stipulate Leibniz's account? We do not need to account for our knowing these truths innately, because that they are necessary truths already provides an adequate explanation.

Not quite sure what to make of all this, but I would appreciate anyone's thoughts.