As someone who works with young people, I’ve been asked more than once whether I believe in the one, or whether every person has some specific other person that they were made to fall in love with and be with forever.*
The one seems to arise from beliefs we treat as self-evident. On the one hand we take each person as unique, unrepeatable, and (when love is involved) unable to be substituted for another; but on the other hand love involves the compatibility and harmony of persons. Since interests arise from the same source as uniqueness, the compatibility of persons must be just as given as their uniqueness. So if persons love – if the utterly unique is also compatible with and in harmony with another – the one exists, Q.E.D.
Stick with the idea for a moment beyond the obvious objections.** So far we have a proof that there is a one for Socrates, but we know nothing about her, nor do we know what we would look for to find her. Shared interests might be one place to look, but harmony of interests is a much more complex thing than shared interests (identical tones don’t harmonize). Say we set researchers to work on finding personal harmonies. The first problem is that they could only identify harmonies on a more general level than the one, and so it might narrow down the field but it could never close it. Even if it could close it, however, we would have the problem that identifying the one by impersonal research is opposed to the proper way in which the one is found. Finding the one in his concrete existence is a different sort of activity than research. It’s harder to imagine a more colossal failure to get the point than telling someone “you are the one for me according to the most reliable research algorithms”.
And so our knowledge of the one develops on a continuum of (a) knowing that there is a one (b) concretizing this idea toward the unreachable limit and (c) whether we’ve gone though a and b or not, we adopt a method of a different kind to find the one as it ought to be found. The first two are impersonal (and therefore inadequate) modes of relating to a person, the last, when viewed as a sort of knowledge, is based on a shared life.
* Most of what gets said in conclusion will have application in theology as well. The argument for the one seems ready made to be turned into a cosmological argument of some kind. That The One was first the God of absolutely apophatic theology is not a coincidence.
(a) This makes way more sense as a reductio ad absurdum against total uniqueness, even in addition to “total uniqueness seeming like a contradiction when said of members of one species or breeding group.
(b) it’s against experience to say we only love one person or even the same sort of person at all times and in all circumstances or
(c) love gets its uniqueness from being made, not given