These lectures trace the activities of warmth, light, and rhythm in the life forms of the natural world. The intent is to form a picture of “the etheric” which is both an important and difficult concept. Moving from an historical look at the idea of the ethers into some of the contributing streams in Rudolf Steiner’s thinking such as the fourth dimension, the nature of warmth and the infinitely distant, and then finally to the current scientific research that supports the idea of the etheric realm.