'The concept of time' presents the reconstructed text of a lecture delivered by Martin Heidegger to the Marburg Theological Society in 1924. It offers an insight into the developmental years leading up to the publication, in 1927, of his magnum opus 'Being and time', itself one of the most influential philosophical works this century. In 'The concept of time' Heidegger introduces many of the central themes of his analyses of human existence which were subsequently incorporated into 'Being and time', themes such as Dasein, Being-in-the-world, everydayness, disposition, care, authenticity, death, uncanniness, temporality and historicity. Starting out by asking - What is time?, Heidegger proceeds to radicalise the concept of time and our relation to it, ending with the question - Are we ourselves time? Am I time?