Our first fallacy springs from the situation just described. It is:
But exactly the distinctive work of science is the modification, the reconstruction, the abandonment of old ideas; the construction of new ones on the basis of observation. This however is a distressing operation, and many refuse to undergo it; even many whose work is the practice of scientific investigation. The old ideas persist along with the new observations; they form the basis--often unconsciously--for many of the conclusions that are drawn.
This is what has occurred in the study of heredity. A burden of concepts and definitions has come down from pre-experimental days; the pouring of the new wine of experimental knowledge into these has resulted in confusion. And this confusion is worse confounded by the strange and strong propensity of workers in heredity to flout and deny and despise the observations of the workers in environmental action; the equally strange and strong propensity of students of environmental effects to flout and deny and despise the work on inheritance. If one accepts the affirmative results of both sets, untroubled by their negations, untroubled by definitions that have come from the past, there results a simple, consistent and useful body of knowledge; though with less pretentious claims than are set forth by either single set.
|The fallacy of non-experimental judgments, in matters of heredity
and development. . . .|
Our second general fallacy is one that appears in the interpretation of observational and experimental results; it underlies most of the special fallacies seen in genetic biology. This is the fallacy that Morley in his life of Gladstone asserts to be the greatest affliction of politicians; it is indeed a common plague of humanity. It is:
|The fallacy of attributing to one cause what is due to many causes. . . .|
|The fallacy of concluding that because one factor plays a role,
another does not; the fallacy of drawing negative conclusions from positive
observations. . . .|
The fallacy that the characteristics of organisms are divisible into two distinct classes; one due to heredity, the other to environment. . . .
|The fallacy of basing conclusions on implied premises that when
explicitly stated are rejected. . . .|
Many premises influencing reasoning are of this hidden, unconscious type. Such ghostly premises largely affect biological reasoning on the topics here dealt with; they underlie several of the fallacies already stated, and several to come. . . .
|The fallacy that showing a characteristic to be hereditary proves that it is not alterable by the environment. . . .|