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13 Darwin and the Scientific Method--Francisco J. Ayala
Pages 267-286

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From page 267...
... What differentiates science from other knowledge is the second episode: subjecting hypotheses to empirical testing by observing whether or not predictions derived from a hypothesis are the case in relevant observations and experiments. A hypothesis is scien tific only if it is consistent with some but not other possible states of affairs not yet observed, so that it is subject to the possibility of falsification by reference to experience.
From page 268...
... Darwin claims to have followed the inductionist canon prevalent among British contemporary philosophers and economists, such as John stuart Mill (1843) , and earlier authorities, notably the statesman and philosopher, Francis Bacon in his Novum Organum (Anderson, 1960)
From page 269...
... (and, indeed, until the zpq9990977820001.g.tif end of his life) , Darwin relentlessly pursued empirical evidence to corroborate the evolutionary origin of organisms and to test his theory of 20p6 natural selection, which he saw as the explanatory process accounting for the adaptive organization of living beings and their diversification and change through time.
From page 270...
... for empirically untestable hypotheses. he wrote of herbert spencer: "his deductive manner of treating any subject is wholly opposed to my frame zpq9990977820002.g.tif of mind.
From page 271...
... . Darwin advanced hypotheses in multiple fields, including geology, plant morphology and physiology, psychology, and evolution, and subjected his hypotheses to severe empirical tests.
From page 272...
... The step from numerous singular statements to a universal one involves logical amplification. The universal statement has greater logical content (it says more)
From page 273...
... The tests to which scientific ideas are subjected include contrasting any hypothesis with the world of experience in a manner that must leave open the possibility that one might reject a particular hypothesis if it leads to wrong predictions about the world of experience. The possibility of empirical falsification of a hypothesis is carried out by ascertaining whether or not precise predictions derived as logical consequences from the hypothesis agree with the state of affairs found in the empirical world.
From page 274...
... it is of the essence of the testing process that the predictions derived from the hypothesis to be tested not be already known, if the observations to be made are to serve as a genuine test of the hypothesis. if a hypothesis is formulated to account for some known phenomena, these phenomena may provide credibility to the hypothesis, but by themselves do not amount to a genuine empirical test of it for the purpose of validating it.
From page 275...
... A contemporary scientist, the nobel Prize recipient François Jacob, has described research in the lab as an interplay between imagination (hypothesis formulation) and experiment: What had made possible analysis of bacteriophage multiplication, and understanding of its different stages, was above all of the play of hypoth eses and experiments, constructs of the imagination and inferences that could be drawn from them.
From page 276...
... The empirical work of scientists is guided by hypotheses, whether explicitly formulated or simply in the form of vague conjectures or hunches about what the truth might be. however, imaginative conjecture and empirical observation are mutually interdependent episodes.
From page 277...
... however, Thomas Cech (1985) and sidney Altman received in 1989 the nobel Prize for independently showing that certain rnA molecules act as enzymes and catalyze their own reactions.
From page 278...
... if the results of an empirical test agree with the predictions derived from a hypothesis, the hypothesis is said to be provisionally corroborated; otherwise it is falsified. The requirement that a scientific hypothesis be falsifiable has been appropriately called the criterion of demarcation of the empirical sciences because it sets apart the empirical sciences from other forms of knowledge (Popper, 1959, 1963)
From page 279...
... if both premises are true, the conclusion falsifying the hypothesis necessarily follows. it follows from this reasoning that it is possible to show the falsity of a universal statement concerning the empirical world; but it is never possible to demonstrate conclusively its truth.
From page 280...
... Darwin occupies an exalted place in the history of Western thought, deservedly receiving credit for the theory of evolution. in The Origin of Species, he laid out the evidence demonstrating the evolution of organisms: 2 chapters dedicated to the geological record, 2 chapters dedicated to biogeography, and 1 chapter dedicated to comparative anatomy and embryology (Darwin, 1859, chapters iX–Xiii)
From page 281...
... , a book that Darwin read as part of his studies at Cambridge University. Paley argued that in the same way that the harmony of the parts making a watch manifest that it had been designed by a skilled watchmaker, so the design of the human eye, with its transparent lens, its retina placed at the precise distance for forming a distinct image, and its large nerve transmitting signals to the brain, manifested to have been designed by the Creator.
From page 282...
... . early in the notebooks of 1837–1839, Darwin registers his discovery of natural selection and repeatedly refers to it as "my theory." From then until his death in 1882, Darwin's life would be dedicated to substantiating natural selection and its companion postulates, mainly the pervasiveness of hereditary variation and the enormous fertility of organisms, which much surpassed the capacity of available resources.
From page 283...
... . Darwin advanced hypotheses in multiple fields, including geology, plant morphology and physiology, psychology, and evolution, and subjected his hypotheses to empirical test.
From page 284...
... There can be little doubt that the causal study of evolution proceeds by the formulation and empirical testing of hypotheses, according to the hypothetico-deductive methodology that is also characteristic of the physicochemical sciences and other empirical disciplines concerned with causal processes. But the study of evolutionary history is also based on the formulation of empirically testable hypotheses.
From page 285...
... Certain biological disciplines relevant to the study of evolution are largely descriptive and classificatory. Description and classification are necessary activities in all branches of science, but play a greater role in certain biological disciplines, such as systematics and biogeography, than in other disciplines, such as population genetics.


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