[dredmorbius]

The Classification doesn't establish unique positions, no, but it serves as the backbone on which those unique call numbers are generated. First the subject and sub-subject classifications, then specific identifiers generally based on title, author, and publication date.

But the detail of the Classification serves the needs and interests of librarians and readers in that you'll, for fairly obvious reasons, need more detail where there are more works, less where there are fewer, and of course changes to reality, as any good contributing editor to The Hitchiker's Guide to the Galaxy (the reference, not D. Adam's charming account loosely linked to it) can tell you, play havok with pre-ordained organisational schemes.

The LoC Classifiction itself is itself only one of these. There are other library classifications, as well as a number of interesting ontologies dating back to Aristotle and including both Bacons, Diderot, encyclopedists of various stripes, and more.