In this seminar, I'll discuss the controls on planetary climate and habitability of planets with liquid water, of which Earth is one example. To do this, I will draw on Earth history, tropical meteorology,  biogeochemical cycling and comparative planetology. Looking at Earth in a wider context is informative to our views of our planet's evolution. Likewise a comparative context Earth's evolution suggests that planetary habitability may be inseparable from inhabitance. To be timely, I'll talk about systematic differences between rotating planets around G-stars (Earth) and tidally locked planets around M-stars (Proxima Centruari b).