Martin Heidegger is infamous for his rejection of the validity of Ethics as a philosophical endeavour ( Letter on Humanism ) and moreover, for his aesthetic formulation of ethos (Holderlin s Hymn The Ister ). This short work will trace the path of Heidegger s thought in his early academic career; from his earliest lectures on Aristotle, Plato, and Religion through to the period in which he published Being and Time. I will argue, along the way, that Heidegger s rejection of the discipline of ethics is founded upon his early work on the notion of 'ethos'. The book will argue that for Heidegger, the notion of ethos is intrinsically tied to the question of grounding; of grounding philosophy on the truth of Dasein's being and as a authentic way of life.