A senseless thing is a thing we don’t understand — a thing that doesn’t make sense to us. Since we are humans with tiny brains and we spend our whole lives hurtling through space on a spinning wet rock, we have countless opportunities to use this word. But we almost never do.
We reserve “senseless” for a certain kind of horrible thing. You’ll never hear us mention a senseless tornado, a senseless shark attack, senseless writing, or a senseless disease.
Almost always, when we use the word “senseless” — senseless cruelty, senseless violence — it’s because people are hurting other people. In a cold, dark universe full of baffling things, this is what confuses us the most.