This article attempts to demonstrate the intelligibility of Bergson's philosophy by analyzing his philosophical method and then applying it to the notions of biological time and of temporal hierarchy in biology. Bergson's philosophical method contains three parts: the first is factual and scientific, the second intuitional and reflective, and the third consists in the formalization and application of intuitive insights. Intuition is not a single act, he insists, but a number of acts, each focussed on a particular level (breadth) of duration. Such acts, focussed on the rhythms of living organisms, can lead to researches in chronobiology like Lecomte du Nouy. Bergson's philosophy, with its diversity of real organisms and levels of process, is more live Whitehead's than has been believed.