A Quote by Jean-Baptiste Dumas
In chemistry, our theories are crutches; to show that they are valid, they must be used to walk... A theory established with the help of twenty facts must explain thirty, and lead to the discovery of ten more.
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Facts and theories are different things, not rungs in a hierarchy of increasing certainty. Facts are the world's data. Theories are structures of ideas that explain and interpret facts. Facts do not go away while scientists debate rival theories for explaining them. Einstein's theory of gravitation replaced Newton's, but apples did not suspend themselves in mid-air pending the outcome.
Theory is worth but little, unless it can explain its own phenomena, and it must effect this without contradicting itself; therefore, the facts are sometimes assimilated to the theory, rather than the theory to the facts.
Scientific theories need reconstruction every now and then. If they didn't need reconstruction they would be facts, not theories. The more facts we know, the less radical become the changes in our theories. Hence they are becoming more and more constant. But take the theory of gravitation; it has not been changed in four hundred years.
Is evolution a theory, a system, or a hypothesis? It is much more it is a general postulate to which all theories, all hypotheses, all systems must henceforward bow and which they must satisfy in order to be thinkable and true. Evolution is a light which illuminates all facts, a trajectory which all lines of thought must follow this is what evolution is.
It must be conceded that a theory has an important advantage if its basic concepts and fundamental hypotheses are 'close to experience,' and greater confidence in such a theory is certainly justified. There is less danger of going completely astray, particularly since it takes so much less time and effort to disprove such theories by experience. Yet more and more, as the depth of our knowledge increases, we must give up this advantage in our quest for logical simplicity in the foundations of physical theory.
Theoretically, we know that the world turns, but in fact we do not notice it, the earth on which we walk does not seem to move andwe live on in peace. This is how it is concerning Time in our lives. And to render its passing perceptible, novelists must... have their readers cross ten, twenty, thirty years in two minutes.
One of the most difficult features of direct experience is that it is unfiltered by any theories or expectations. It's hard to observe without imposing a theory to explain what we're seeing, but the trouble with theories, as Einstein said, is that they explain not only what is observed, but what can be observed. We start to build expectations based on our theories.
No theory ever agrees with all the facts in its domain, yet it is not always the theory that is to blame. Facts are constituted by older ideologies, and a clash between facts and theories may be proof of progress. It is also a first step in our attempt to find the principles implicit in familiar observational notions.
I am more fond of achieving than striving. My theories must prove to be facts or be discarded as worthless. My efforts must soon be crowned with success, or discontinued.
All good intellects have repeated, since Bacon's time, that there can be no real knowledge but that which is based on observed facts. This is incontestable, in our present advanced stage; but, if we look back to the primitive stage of human knowledge, we shall see that it must have been otherwise then. If it is true that every theory must be based upon observed facts; it is equally true that facts can not be observed without the guidance of some theory. Without such guidance, our facts would be desultory and fruitless; we could not retain them: for the most part we could not even perceive them.
It is ... a sign of the times-though our brothers of physics and chemistry may smile to hear me say so-that biology is now a science in which theories can be devised: theories which lead to predictions and predictions which sometimes turn out to be correct. These facts confirm me in a belief I hold most passionately-that biology is the heir of all the sciences.
To no circumstance is the wide diffusion of error in the world more owing than to our habit of adopting conclusions from insufficiently established data. An indispensable preliminary, then, in every investigation, is to get at facts. Until these are arrived at, every opinion, theory, or system, however ingeniously framed, must necessarily rest upon an uncertain basis.
Is evolution a theory, a system, or an hypothesis? It is much more: it is a general condition to which all theories, all hypotheses, all systems must bow and which they must satisfy henceforward if they are to be thinkable and true.
If the experiments which I urge be defective, it cannot be difficult to show the defects; but if valid, then by proving the theory, they must render all objections invalid.
Well-established theories collapse under the weight of new facts and observations which cannot be explained, and then accumulate to the point where the once useful theory is clearly obsolete.
If facts conflict with a theory, either the theory must be changed or the facts.
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