It is hard to think of two thinkers who have had a greater influence on contemporary philosophy of science. Their main insight is that it is impossible to investigate the nature of reality without operating with some mental paradigm or other, usually assumed by scientists but not scientifically provable, and therefore we should see science as nothing more than the evolution of ideas paralleling the evolution of organisms.

Popper was twenty years Kuhn’s senior and is perhaps best known for his The Logic of Scientific Discovery (1934), The Open Society and its Enemies (1945), and Conjectures and Refutations (1963). They are considered among the most important philosophical works of the 20th century. The first one sets out his theory of “falsification” (which we shall explore further down) together with topics such as theories, probability, corroboration, and quantum theory. The second defines the “open society” as one which allows its citizens to examine and put forward a wide range of differing proposals, followed by unbiased criticism, followed by the making of any necessary changes to benefit the common good of society.

In this book Popper offers a severe critique of the totalitarian society advocated by Plato and Marx. To his mind, those societies preclude the openness he advocates by claiming knowledge that they cannot possibly have and then obliging others to submit to it. In the third book Popper applies falsificationism to both the philosophy of science and political philosophy.

Falsificationism gave rise to a whole new area of debate in the philosophy of science. It claims that the mark of a scientific theory is whether it makes predictions which could in principle serve to falsify it. The more such predictions a theory makes, the better it is. This is Popper’s response to what he calls “the myth of induction.” As characterized by Hume, induction is the method of arriving at theories, laws or generalizations by observing regularities in experience. Popper agrees with Hume that any generalization goes beyond the possible evidence for it. No number of observed cases of some A having property B allows the conclusion that all As have that property. That is mere conjecture and speculation. One cannot possibly observe all As to justify an unassailable conclusion.

So the first fallacy of this characterization assumes erroneously that scientific generalizations are conclusions. The second fallacy is that it fails to describe accurately the process by which scientists go about forming hypotheses. Rather than being conclusions inferred from evidence, those generalizations have the logical status of mere conjectures. They are tentative hypothesis on trial in “the court of experience.” Thus Hume’s problem of induction disappears because generalizations are not supported or justified by observation. On the contrary, generalizations are logically prior, being first conjectured and then either refuted by experience (when some A is found which lacks property B), or survive to await further observation of As. So experience can never verify a theory as true, only falsify it. Generalizations are first conjectured, then held up to the scrutiny of experience for refutation.

Closely tied to Popper’s conception of science as generating theories capable of falsification is his attack on the dialectics of Marx and Hegel, such theories seem immune from empirical falsification, since any experience can be accounted for by some suitable interpretation of the doctrine. Popper finds particularly outrageous that Marxism explicitly claims to be a science. He is equally scathing of both Plato and Freud whom he also dubs as enemies of the open society.

Popper’s influence has furthered many debates in the philosophy of science and undoubtedly inspired the work of Thomas Kuhn who is best known for his seminal work titled The Structure of Scientific Revolutions which he wrote as a graduate student in theoretical physics at Harvard University in the early sixties. Kuhn was dismayed by the simplistic rationalistic accounts that modern philosophers gave of the history of science as a continually progressive subject edging ever closer to the truth. Kuhn challenged the idea of continuous, if not outright deterministic progress. He saw radical discontinuities between different periods of scientific investigations.

Kuhn argues that the history of science is punctuated by violent intellectual revolutions overturning long periods of rather conservative puzzle-solving. He saw periods of so called “normal” science as characterized less by independent and objective research than by adherence to some agreed assumptions and expected outcomes. Paradoxically, the scientists begin to look like a priesthood of a faith called science wherein everything can be doubted except the faith itself. During these periods of normal science, unexpected findings often get brushed aside as irrelevant and original research which in any way questions the current assumptions of “orthodox” theory are debunked as useless speculation.

Thus we arrive at Kuhn’s most original notion, that of the paradigm; that is to say, the web of interwoven assumptions and beliefs, a faith of sort, shared by a particular community which underlies and sets the agenda for the current research. As per Kuhn, only results which tend to strengthen the current paradigms get accepted during periods of normal science. What is highly intriguing in the process is that the paradigm itself is never questioned or criticized. However, from time to time paradigms are challenged and overthrown by intellectual revolutions. When the current paradigm fails to provide adequate models for observed phenomena a paradigm-shift takes place and a new more powerful model which has greater explanatory force takes its place. For example, Copernicus’ heliocentric theory of the Solar system will replace the Ptolemaic idea that the sun revolves around the earth, or Einstein’s theory of relativity and quantum mechanics will replace Newton’s theory of gravity, space and motion.

When this paradigm shift takes place, the scientists’ view of the world is so radically altered that old and new are qualitatively and quantitatively incomparable. It is as if a new “myth” of making sense of reality arrives on the scene. One is bound to muse whether or not the Western mind makes sense of reality via “the myth of science” while other cultures use different myths and explanatory paradigms. To wrap one’s mind around that concept however requires that one adjusts one’s understanding of the meaning of “myth” as being much more than a mere cute lie about reality to tell children.

Be that as it may, from these observations Kuhn derives the notion of “incommensurability” which challenges the notion that science is on an advancing path of unstoppable progress toward ultimate truth. The undeniable fact, Kuhn points out, is that scientists operating at different theoretical periods with different paradigms live in psychologically different worlds. The world of Ptolemy is not the same world as Copernicus. When Ptolemy observes the sun he observes an object that move around the earth, whereas Copernicus sees the central star of the solar system.

So what are the implications for science’s usurpation from philosophy of the idea of absolute truth? For both Popper and Kuhn it is a questionable notion that science ought to do without as it attends to its own proper domain which is not that of metaphysics or theology but mere observation of phenomena and its laws. Given that it is impossible to investigate the nature of reality without operating with some paradigm or other, it is wiser by far to see science as the evolution of ideas in response to the phenomena of the world. Vico for one recommends that man can know much more of what he himself has made (language, institutions, history) than about nature which he certainly has not made as a creature. Indeed, if we think of the evolution of ideas in much the same way as the evolution of organisms, then there is no more reason to believe ideas are evolving towards some ultimate truth, just as there is no reason to think that organisms are evolving towards some ultimate being.

Some of course are not persuaded even when science assumes a more humble stance as suggested by Popper and Kuhn. They are not impressed by a purposeful universe with no overarching intentionality. From the grandeur of the universe revealing an intelligent design, they conclude that just as it is absurd to find a watch in the street and to proclaim that it came together by itself; it is equally absurd to observe a design in the universe and fail to see that it points to a Maker who created it all with one Word understood as the “logos” or its meaning. Western philosophy begins with the idea of an orderly and meaningful universe.

As Kant famously put: two sublime phenomena of the universe are the starry sky above me and the moral law within me. There seems to be an intimation of a connection between the starry night above and the moral law within, as Wordsworth and Coleridge’s poetics of “intimations of immortality” powerfully suggest. And so the dialogue goes among honest men of good will, impelled by a courageous and unbiased examination of both sides of the argument on science vis a vis a vis truth, for more than his will to power what ultimately impels man is his will to truth.