Quantum mechanics forbids a quantum system from being both knowable and objectifiable. But quantum mechanics and quantum field theory assume that the spacetime metric is both knowable and objectifiable. If the metric is not knowable or not objectifiable, then it’s impossible to define a quantum theory precisely. In that sense it seems like the term “quantum gravity” is oxymoronic. String theory demands that the graviton exist, but so far it hasn’t enlightened us on the ultimate resolution of this apparent oxymoron.