Metaphysical convergence is when the same conclusion or idea occurs in different metaphysical systems but is reached by a derivation from different sets of principles. I chose convergence because of the similarity to convergent evolution, when species evolve similar features, though they are not closely related in terms of a recent common ancestor.

In a post at the end of October, "Man and woman is primary - masculine and feminine are secondary abstractions" Bruce Charlton writes:

"*the soul of a Man is either a man's or a woman's soul. This is a fact that carries-through whatever happens in mortal life - which carries through attributes, biology, psychology and social roles.*"

I commented, saying that Virgil seems to have thought something similar because in the *Aeneid*, Aeneas encounters the soul of Caeneus in the underworld:

"*Caeneus, once a youth, now a woman, and again turned back by Fate into her form of old.*"

Although Caeneus turned into a man physically, the soul was a woman's soul.

Bruce Charlton responded by saying:

"*Well, Virgil certainly did not have the metaphysical assumptions which I do. Presumably this is a specific coincidence of conclusions, rather than the same baseline reality.*"

And this is an interesting fact if you think about it. Here we have two fairly different metaphysical foundations giving the same conclusion.

One way I find this helpful to think about is by drawing connections to mathematics. For instance, it is well-known that in addition to the familiar Euclidean geometry, there is also Non-Euclidean geometry, which was discovered when it was realized that the parallel postulate could be replaced with two different postulates, each of which gave consistent geometries. But in addition, there is also absolute geometry, which consists of those geometric facts which do not depend on the parallel postulate for their proof and hence are true in both Euclidean and Non-Euclidean geometry.

The analogy is that we may have a set of metaphysical assumptions where if one or more are changed, then we can derive completely a different metaphysics from the new assumptions. This is expected, but what is also interesting is that there may be some conclusions that hold between both sets of assumptions.

Another situation that might happen is when different metaphysical systems give different justifications for the same conclusions. They both reach the same place by a different route.

Also interesting is, the parallel postulate article lists many statements that are mathematically equivalent to the parallel postulate. Mathematically equivalent does not necessarily mean that they are saying exactly the same thing, but rather means that given the parallel postulate and the rest of the Euclidean axioms, one can prove the equivalent statement. And, conversely, given the equivalent statement, and the other axioms, one can derive the parallel postulate. Two mathematically equivalent statements stand or fall together, if one is true, then so is the other and if one is false, then the other is as well.

And there may be something similar in metaphysics as well, metaphysical assumptions that also stand or fall together.

Another possibility is metaphysical independence. Just as the parallel postulate is independent of the other axioms of Euclidean geometry, that is, they can neither prove it nor disprove it, there may be questions that can be asked within any particular metaphysics that can neither be concluded true nor false within this metaphysics. More assumptions are needed.

One could call the study of different metaphysical systems and how they relate meta-metaphysics, perhaps.

I do not have any particular thoughts on these matters in this post, but I believe that thinking about these kinds of things could be useful. I am curious if any readers have any thoughts about or examples of metaphysical convergence or other matters in meta-metaphysics.