1. Francis Bacon, Novum Organum, 1620

Hamblin considers Francis Bacon’s New Organon as a psychological turning point in the conception of fallacies (Hamblin 1970, p. 146; Walton, 1999). Bacon presents his concept of “idol” as the scientific counterpart of logical or dialectical fallacies. An idol is an obstacle to the (inductive) edification of scientific knowledge.

The word idol comes from a Greek term meaning “simulacrum, phantom” (Bailly, [eidolon]). According to Bacon, a fallacy is a simulacrum, a phantom of argument, produced under the influence of towering idols, defined as false Gods altering human reasoning:

XXXIX. Four species of idols beset the human mind, to which (for distinction’s sake) we have assigned names, calling the first Idols of the Tribe, the second Idols of the Den, the third Idols of the Market, the fourth Idols of the Theater. ([1620], p. 20)

— The Idols of the Tribe, that is of the whole of humanity. These idols are the deformations imposed upon reality by the innate structure of the human mind, which is not a tabula rasa but an “uneven mirror” (id.). Its a priori categories distort reality.

— The Idols of the Den are the product of the education and history of each individual, that is to say, prejudices or other evidences, exerting their powers through “Authority” (id., p. 21).

— The Idols of the Market place are the words themselves, which “still manifestly force understanding, throw everything into confusion, and lead mankind into vain and innumerable controversies and fallacies” (id., p. 21).

— The Idols of the Theater correspond to “the various dogmas of peculiar systems of philosophy, and also from the perverted rules of demonstration” (id., p. 22).

These Idols include fallacious inferences as well as substantial fallacies.

2. John Locke, An Essay Concerning Human Understanding, 1690

In a brief section of his Essay, Locke reflects “on four sorts of arguments, that men in their reasonings with others, do ordinarily make use of to prevail on their assent or at least so to awe them as to silence their opposition” ([1690], p. 410). This definition of an argument perfectly suits what is a rhetorical argument as pressure exerted on the audience, S. Logos – Ethos – Pathos. These four sorts of arguments are (id., p. 410-412):

“The argumentum ad verecundiam”, S. Modesty
“The argumentum ad ignorantiam”, S. Ignorance
“The argumentum ad hominem”, S. Ad hominem
“The argumentum ad judicium”, S. Matter.

Locke rejects the first three arguments on the ground that, at best, they “may dispose me, perhaps, for the reception of truth, but help me not to it”:

For, 1. It [ad verecundiam] argues not another man’s opinion to be right because I, out of respect, or any other consideration but that of conviction, will not contradict him. 2. It [ad ignorantiam] proves not another man to be in the right way, nor that I ought to take the same way, because I know not a better. 3. Nor does it follow that another man is in the right way because he has shown me that I am in the wrong. I may be modest, and therefore not oppose another man’s persuasion; I may be ignorant, and not be able to produce a better; I may be in error, and another may show me that I am so. This may dispose me, perhaps, for the reception of truth, but helps me not to it (id., 411).

The concept of fallacy is redefined independently of any Aristotelian consideration. The only valid arguments are arguments ad judicium, that is to say “proofs drawn from any of the foundations of knowledge or probability” (ibid.); truth “must come from proofs and arguments and light arising from the nature of things themselves” (id., 412). Note that whilst the fallacious arguments correspond to argument schemes, the argument ad judicium does not correspond to just one argument scheme but to any kind of argument recognized as scientifically valid.

Leibniz ([1765]) nuanced this strict vision of fallacious arguments (see the above mentioned entries).