For decades, a lemon-yellow organism called Physarum polycephalum has been quietly dismantling one of humanity's most cherished assumptions — that intelligence belongs to those who possess a brain. Scientists now find themselves sharply divided over whether slime moulds, plants, and even individual cells demonstrate genuine cognition, or whether applying such language to brainless life forms empties the words of all meaning. The dispute is not merely academic; it asks whether intelligence is a rare crown worn by animals, or a thread woven through the fabric of life itself.