The reader will readily appreciate what this title meant for me. In the circles where my work lay, an intense controversy was just then raging round Einstein's ideas. I usually took sides with the supporters of Einstein, for it seemed to me that Einstein had carried the existing mode of scientific thinking to its logical conclusions, whereas I missed this consistency among his opponents. At the same time I found that the effect of this theory, when its implications were fully developed, was to make everything seem so 'relative' that no reliable world-outlook was left. This was proof for me that our age was in need of an altogether different form of scientific thinking, equally consistent in itself, but more in tune with man's own being.