The rise of the natural sciences is credited with a demonstrable, ever-quickening increase in human knowledge and power; shortly before the modern age European mankind knew less than Archimedes in the third century B.C., while the first fifty years of our century have witnessed more important discoveries than all the centuries of recorded history together. Yet the same phenomenon is blamed with equal right for the hardly less demonstrable increase in human despair or the specifically modern nihilism which has spread to ever larger sections of the population, their most significant aspect perhaps being that they no longer spare the scientists themselves, whose well-founded optimism could still, in the nineteenth century, stand up against the equally justifiable pessimism of thinkers and poets. The modern astrophysical world view, which began with Galileo, and its challenge to the adequacy of the senses to reveal reality, have left us a universe of whose qualities we know no more than the way they affect our measuring instruments, and — in the words of Eddington — "the former have as much resemblance to the latter as a telephone number has to a subscriber." Instead of objective qualities, in other words, we find instruments, and instead of nature or the universe — in the words of Heisenberg — man encounters only himself.

[The German physicist Werner Heisenberg has expressed this thought in a number of recent publications. For instance: "Wenn man versucht, von der Situation in der modernen Naturwissenschaft ausgehend, sich zu den in Bewegung geratenen Fundamenten vorzutasten, so hat man den Eindruck, ... dass zum erstenmal im Laufe der Geschichte der Mensch auf dieser Erde nur noch sich selbst gegenübersteht ... , daß wir gewissermassen immer nur uns selbst begegnen" (Das Naturbild der heutigen Pkysik [1955], pp. 17-18). Heisenberg's point is that the observed object has no existence independent of the observing subject: "Durch die Art der Beobachtung wird entschieden, welche Züge der Natur bestimmt werden und welche wir durch unsere Beobachtungen verwischen" (Wandlungen in den Grundlagen der Naturwissenschaft [1949], p. 67).]
"Vita Activa"