What is metaphysics in relation to language? Is language a subset of metaphysics, or is metaphysics a subset of language, and if not what is language or metaphysics in relation to the other, and why is it difficult to represent those two in a sort of Venn diagram? Sounds like a dumb question, but I have trouble answering and I can't figure out why.
Trivially, the set of all metaphysical statements is a subset of all articulated language statements.
However, metaphysics is essentially an academic discipline. By extension, metaphysics is the collection of theoretic views articulated by metaphysicians.
On the other side, language may be seen as the structure of verbal communication, that is, what is relatively stable in the verbal communication of one community of speech.
So there is no formal relation between metaphysics and language, and one is not a subset of the other.
Metaphysical theories require some language to be articulated.
All natural languages are used initially to communicate about what people believe that there is, which you could argue is precisely the subject matter of metaphysics, namely, being.
There is also no essential formal difference between statements made in everyday life and theoretic statements made in the context of metaphysics or of any formal science. To say that you have a sandwich in the fridge, or to say that there is a prime number less than 10 etc. is to make what is fundamentally a metaphysical statement, a statement about being. Even a fiction is just a statement about imaginary beings. The whole of mathematics is the collection of statements about conceptual beings using some mathematical language.
So, you could argue that metaphysics is just an effort to articulate what everybody says about what there is although in one unified and more coherent theoretic whole.
This is more general than that. Any science could be understood as already present in everyday life since the beginning of humanity. Science is just more systematic, more organised, more coherent etc. than everyday practice. Every individual science just emerged as a specialisation on one aspect of everyday expertise.
So you could always make connections, but these are trivial because not specific to metaphysics. There are also as many metaphysical beliefs as there are humans, although this is somewhat limited by human imagination.
The really profound connection is that human thought, and so verbal communication, and so verbal statements, is about what there is. The animal brain can be seen as a cognitive system dedicated to deciding what there is, even though, in effect, a brain can only possibly know what there is inside itself. But this is what makes any metaphysical statement inherently speculative.
Metaphysics is about the basic ontological categories in the world. Things like space, time, matter, cause and effect, motion, change and God.
Because reasoning about such basic categories is not easy, metaphysics has gained a bad reputation. And even more so in the contemporary intellectual world, which being so militantly athiest, sees anything that has the slightest whiff of the supernatural, and I mean this in its non-pejorative use, as being above nature, as frankly medieval, outmoded and deeply unfashionable as well as being unscientific and just so plain stupid that only stupid people can give it any credence. You get the picture.
In none of these categories listed above does language figures as a basic ontological category. After all, its easy enough to imagine a universe without life, and hence no language; but its much harder to conceptualise what a world without space or time might look like.
Neverthless, I would argue that language is a basic ontological category. In the same way that minds are. Not all basic ontological categories must be basic in the same way as matter or space is. What is basic about it is that it is very different in kind from the others listed above.