In the 1950s, there was a hot debate among ecologists about what regulates animal populations so as to keep them persisting for a long time. The participants of the debate were divided into two schools of thought, one insisting on the importance of climatic factors and the other emphasizing the necessity of density-dependent biotic factors. Albeit an important subject, no clear answers came out of the debate. A fundamental problem in the indecisive debate lay in the lack of clear definitions of ‘regulation’ and ‘persistence’ of populations. Consequently, the current ecological thoughts inherit many myths and ambiguities about the nature of population regulation. Here, I delve into the subject to look for unambiguous answers. In particular, I show that a climatic (density-independent) control of populations is theoretically possible but fragile in a fluctuating environment, and that density-dependent regulation is necessary but not sufficient for keeping populations in the persistent state.