Yes. He was indeed a ṛṣi. But what kind of a ṛṣi was He? What was his expertise? From that wiki article you mentioned, it's obvious Kaṇāda pioneered the Vaiśeṣika vāda school, one of the Ṣaḍ Darśanas | 6 major Philosophies in Hinduism. Nevertheless, due to his (exalted) rank he was that of a seer, hence the prefixed title of « Maharṣi » to his name Kaṇāda i....
Maharishi Kanada talks about the relationship between cause and effect in the following Shlokas:
कारणभवात् कार्य्याभावः ।। १ । २ । १ ।।
कारणभवात् (Kaaranabhaavaat), from the non-existence of cause
कार्य्याभावः (Kaaryyabhaavah), non-existence of effect
Non-existence of effect (follows) from the non-existence of cause