Enlightenment, understood in the widest sense as the advance of thought, has always aimed at liberating human beings from fear and installing them as masters. Yet the wholly enlightened earth is radiant with triumphant calamity. Enlightenment’s program was the disenchantment of the world. It wanted to dispel myths, to overthrow fantasy with knowledge. Bacon, “the father of experimental philosophy,” brought these motifs together. He despised the exponents of tradition, who substituted belief for knowledge and were as unwilling to doubt as they were reckless in supplying answers. All this, he said, stood in the way of “the happy match between the mind of man and the nature of things,” with the result that humanity was unable to use its knowledge for the betterment of its condition. Such inventions as had been made—Bacon cites printing, artillery, and the compass—had been arrived at more by chance than by systematic enquiry into nature. Knowledge obtained through such enquiry would not only be exempt from the influence of wealth and power but would establish man as the master of nature. 
I shall now very briefly criticize Bacon’s anti-theoretical dogma and his view of science […].
1. The idea that we can purge our minds of prejudices at will and so get rid of all preconceived ideas or theories, prior to, and preparatory to, scientific discovery, is naïve and mistaken. It is mainly through scientific discovery that we learn that certain of our ideas such as those of the flat earth or the moving sun are prejudices. We discover the fact that one of the beliefs we held was a prejudice only after the advance of science has led us to discard it. For there is no criterion by which we could recognize prejudices in anticipation of this advance.
2. The rule ‘Purge yourself of prejudice!’ can therefore have only the dangerous result that, after having made an attempt or two, you may think that you have succeeded – with the result, of course, that you will stick more tenaciously to your prejudices and dogmas, especially to those of which you are unconscious.
3. Moreover, Bacon’s rule was ‘purge your mind of all theories!’ But a mind so purged would not only be a pure mind: it would be an empty mind.
4. We always operate with theories, even though more often than not we are unaware of them. The importance of this fact should never be played down. Rather, We should try, in each case, to formulate explicitly the theories we hold. For this makes it possible to look out for alternative theories, and to discriminate critically between one theory and another.
5. There is no such thing as a ‘pure’ observation, that is to say, an observation without a theoretical component. All observation – and especially all experimental observation – is an interpretation of facts in the light of some theory or other. 
Bacon’s observationism and his hostility to all forms of theoretical thought were revolutionary, and were felt to be so. They became the battle cry of the new secularized religion of science, and its most cherished dogma. This dogma had an almost unbelievable influence upon both the practice and the theory of science, and this influence is still strong in our own day. 
Science begins with observation, says Bacon, and this saying is an integral part of the Baconian religion. It is still widely accepted, and still repeated ad nauseam in the introductions to even some of the best textbooks in the field of the physical and biological sciences.
I propose to replace this Baconian formula by another one.
Science, we may tentatively say, begins with theories, with prejudices, superstitions, and myths. Or rather, it begins when a myth is challenged and breaks down – that is, when some of our expectations are disappointed. But this means that science begins with problems, practical problems or theoretical problems. 
In the past, the term ‘induction’ has been used mainly in two senses. The first is repetitive induction (or induction by enumeration). This consists of often repeated observations and experiments, which are supposed to serve as premises in an argument establishing some generalization or theory. The invalidity of this kind of argument is obvious: no amount of observation of white swans establishes that all swans are white (or that the probability of finding a non-white swan is small). In the same way, no amount of observed spectra of hydrogen atoms on earth establishes that all hydrogen atoms emit spectra of the same kind. Theoretical considerations, however, may suggest the latter generalization, and further theoretical considerations may suggest that we should modify it by introducing Doppler shifts and Einsteinian gravitational redshifts.
Thus repetitive induction is out: it cannot establish anything.
The second main sense in which the term ‘induction’ has been used in the past is eliminative induction – induction by the method of eliminating or refuting false theories. This may look at first sight very much like the method of critical discussion that I am advocating. But in fact it is very different. For Bacon and Mill and other exponents of this method of eliminative induction believed that by eliminating all false theories we can finally establish the true theory. In other words, they were unaware of the fact that the number of competing theories is always infinite – even though there are as a rule at any particular moment only a finite number of theories before us for consideration. [104-5]
The Large Hadron Collider is the most complicated scientific experiment ever built. But it’s still just an experiment like any other. At its heart, there is repeatable process, as with Newton’s prism. There are teams of people dedicated to making detailed measurements, as Cavendish did with his flammable air. And the same rigorous logical thought processes used by Bill Tutte are of course applied here too. These are simple principles, yet they hold great power. [51:15]
There’s table after table of results. But he also describes precisely how he got those results. There’s a beautiful diagram of his apparatus, and this is there so that anyone else reading this paper, if they’re sceptical about the results or even if they just want to check them, can rebuild the apparatus and redo the experiment and check that Tyndall didn’t make any mistakes.
So these results are not a matter of opinion: they’re here, they can be checked by other scientists, they can be verified. So this is how scientific knowledge progresses. Publishing is the reason why science gets to our best view of the way that nature works. [43:28]
The common explanation for the appearance of the colours was that they were added by impurities in the prism to the pure white light. Newton thought that the colours were already present in the white sunlight. But what set Newton apart was that he devised and performed an experiment to test his hypothesis. …
Green light into the prism equals green light out. That implies that the colours themselves are pure. The prism is not subtracting or adding anything. That means that Newton’s hypothesis was shown to be correct. …
Newton was one of the first to interrogate Nature using the principles of what we now call the scientific method. In other words, he observed the world, came up with theories to explain what he saw, then tested them with experiments to see if he was right. The power of this approach is that it aims to remove preconceived ideas and, in doing so, deliver a more accurate description of the natural world. [7:40]
[G]athering evidence and building arguments from what can be seen and reproduced is at the heart of a modern scientist’s work. 
Darwinian evolution is the most robust of scientific theories, but many people find it easier and more reassuring to believe that something so intricately constructed as life on Earth must have had a designer. It is hard for us to accept that erverything around us, from the beautry of the butterfly to the complexity of the human eye, could have evolved simply through chance and the pressure to survive. But the scientific evidence that evolution by natural selection has occurred is unassailable.
The scientific method, which is today practised in all corners of the globe, builds on explanations based on evidence, and when new evidence emerges that does not fit with the model, the explanation must change. That is how science moves on.