Sir Karl Popper: On the So-Called Sources of Knowledge (Excerpt)
1. There are no ultimate sources of knowledge. Every source, every suggestion, is welcome; but every source, every suggestion, is also open to critical examination. As long as we are not dealing with historical matters, we usually examine the asserted facts themselves, rather than investigate the sources of our information.
2. The proper questions of epistemology are not actually concerned with sources at all; rather, we ask whether an assertion is true – that is to say, whether it agrees with the facts. In connection with this critical examination of the truth, all kinds of arguments may be brought to bear. One of the most important procedures is to take a critical attitude towards our own theories and, in particular, to look for contradictions between our theories and observations.
3. Tradition is – apart from inborn knowledge – by far the most important source of our knowledge.
4. The fact that most of the sources of our knowledge are traditional demonstrates that opposition to tradition, that is to say, antitraditionalism, is of no importance. But this fact must not be held to support traditionalism; for every bit, however small, of our traditional knowledge (and even of our inborn knowledge) is open to critical examination and may be overthrown if need be. Nevertheless, without tradition, knowledge would be impossible.
5. Knowledge cannot start from nothing – from the tabula rasa – nor yet from observation. The advance of our knowledge consists in the modification and the correction of earlier knowledge. Of course it is sometimes possible to take a step forward through an observation or through a chance discovery; but the significance of an observation or of a discovery generally depends upon whether it enables us to modify existing theories.
6. Neither observation nor reason is an authority. Other sources, such as intellectual intuition and intellectual imagination, are most important, but they are also unreliable: they may show us things with the utmost clarity and yet mislead us. They are the main sources of our theories and are therefore indispensable; but the vast majority of our theories are false. The most important function of observation and logical thought, but also of intellectual intuition and imagination, is to help us in the critical examination of those bold theories which we need in order to delve into the unknown.
7. Clarity is an intellectual value in itself; exactness and precision, however, are not. Absolute precision is unattainable; and there is no point in trying to be more precise than our problem demands. The idea that we must define our concepts to make them ‘precise’ or even to give them a ‘meaning” is misleading. Every definition must make use of defining concepts; and so we can never ultimately avoid working with undefined concepts. Problems connected with the meaning or the definition of words are unimportant. Indeed, these purely verbal problems are tiresome: they should be avoided at all costs.
8. Every solution of a problem creates new unsolved problems. The harder the original problem and the bolder the attempt to solve it, the more interesting these new problems are. The more we learn about the world, and the deeper our learning, the more conscious, clear and well-defined will be our knowledge of what we do not know, our knowledge of our ignorance. The main source of our ignorance lies in the fact that our knowledge can only be finite, while our ignorance must necessarily be infinite.
We get an idea of the vastness of our ignorance when we contemplate the vastness of the heavens. It is true that the size of the universe is not the deepest cause of our ignorance; but it is nevertheless one of its causes.
I believe that it is worthwhile trying to discover more about the world, even if this only teaches us how little we know. It might do us good to remember Rom time to time that, while differing widely in the various little bits we know, in our infinite ignorance we are all equal. If we thus admit that there is no authority beyond the reach of criticism to be found within the whole province of our knowledge, however far we may have penetrated into the unknown, then we can retain, without risk of dogmatism, the idea that truth itself is beyond all human authority Indeed, we are not only able to retain this idea we must retain it. For without it there can be no objective standards of scientific inquiry; no criticism of our conjectured solutions, no groping for the unknown, and no quest for knowledge.
Lecture delivered to the University of Salsburg 27 July 1979. From In Search of a Better World. London: Routledge 1984.