Bacon's positive idea of progress has its negative complement in iconoclasm directed against whatever impeded the advance of science. His famous doctrine of Idols illustrates this iconoclasm and the workings of his mind.
'Idols' is a term which he used figuratively for fallacies which block or distort men's perception of reality and their pursuit of truth. They are psychological barriers — pre-possessions, prejudices, and delusions, emotional and sentimental biases. In short, they include all the imaginings which prevent men from seeing the object as it really is.
Bacon's concept of Idols did not develop at one time or in a step-by-step progression, but flexibly: in different works he shifted his emphasis and classifications, discarding, exploring, and revising as he searched for the most accurate and most elective formulation of the doctrine; or perhaps it would be more just to state that he knew that no single systematisation of words and ideas could perfectly describe and correspond to what he was trying to communicate. Moreover, it was typical of him to change and experiment with ideas and their arrangement. His theories undergo transformations kindred to the forms which fluctuate within a total pattern in Baroque art. Bacon imposes order on his ideas, but within his systems there is flux and movement suggestive of the spiralling found in Baroque architecture. Thus his ideas on Idols circle and rise and develop from work to work in a manner which might be diagrammed as a zigzag mounting within a spiral. In The Male Birth of Time (1593 ?), he mentions three kinds of Idols, those of the Theatre, Market-place, and Cave, and suggests another division between Idols of the Home and of the Highway, but gives no explanation of what they all mean. In Valerius Terminus (1585?), he gives a fourfold classification, substituting 'Palace' for 'Market-place' and adding Idols of the Nation or Tribe. But in the Advancement he reverts to a triple system and presents modified concepts of Idols of the Tribe, Cave and Market-place, or Palace though he does not employ those terms; and, in a marginal note, he divides Idols into the native and the adventitious. This last distinction was developed along with a new one in 1607, and the doctrine took other forms in later works before it reached its fullest description in the New Organon.
The following account will be confined to influential aspects of the doctrine regardless of its variations.
Suppose that an ancient Greek philosopher's natural human tendency to correct and unify led him to mistake a man standing beside a horse for a creature with a human head and an equine body, that is, a centaur. Some of the philosopher's friends might believe his report because of his authority, others because of its novelty. Their accounts of the centaur might be read centuries later and accepted as true because of their antiquity or because belief in the existence of centaurs had become common. Some profound mind might then argue from this instance that there must be a like combination of man with bull or lion or elephant; and a philosopher might then formulate a principle of animal cohesion or a doctrine that the soul resides in the upper part of the human body.
These seven fallacies are examples of Idols. In the Advancement Bacon cautions against them:
for the mind of man is far from the nature of a clear and equal glass, wherein the beams of things should reflect according to their true incidence; nay, it is rather like an enchanted glass, full of superstition and imposture, if it be not delivered and reduced.
Bacon stated in Valerius Terminus that he found in this enchanted glass
'four Idols or false appearances . . . every sort comprehending many divisions'.
In Novum Organum he explained them in the following order:
Idols of the Tribe are mental characteristics common to all men such as the tendency to find order and regularity where it is lacking (as in the instance of the Greek who thought he saw a centaur), the proneness of men to allow their desire, pride, prejudice, hopes, and prepossessions to blind them to realities; and men's inclination to trust their five senses, despite their fallibility, without enlisting the help of experiments:
Idols of the Cave are the fallacies imposed on individuals by the limitations of their peculiar natures, environments, and experiences. Each man lives in a world of his own, confined, as it were, to a cave, lacking reliable knowledge of what exists outside it. As a result he is likely to see things not as they are but distorted by his idiosyncrasies and specialties. Thus a musician may think that the soul is only a harmony. In Bacon's opinion, William Gilbert, his contemporary, had over-specialised in the study of magnetism to such a degree that he erred in trying to formulate a whole philosophy in terms of it. Bacon therefore advised students to hold in suspicion any idea which particularly appealed to them:
'Idols of the Market place are the most troublesome of all'. They are semantic fallacies, notions imposed on the mind by words which 'entangle and pervert the judgement'. They are either names of things which do not exist or inaccurate and confused names for existent things. Of the former kind are 'fictions which owe their origin to false and idle theories', such as the notion that the goddess Fortune governs men's destinies. Examples of distorting and ill-defined words are not far to seek in the modern world of advertising and doubletalk, when 'true democracy' has different meanings in Russia, England, and Cuba, and a buyer is at a loss to know what is meant by 'Guaranteed Pure' printed on a label. Bacon concludes that
'It is not possible to divorce ourselves from these fallacies and false appearances, because they are so inseparable from our nature and condition of life,'
but we must guard against them.
Idols of the Theatre are systems of dogma or philosophy which have been invented with little or no regard to realities: they resemble the fictions of stage plays which distract audiences from what is to illusory worlds. Such systems may be sophistical, extracting a great deal from a few facts, or empirical, extracting a little from many things, or superstitions, mixing philosophy with theology and tradition. All of these are errors because they do not see knowledge truly. The Sophists do not consult experience; the Empiricists are too easily satisfied; and the Superstitious contaminate knowledge and spread their fallacies widest of all. The Idols of the Theatre also influence the mind into excesses of dogmatism or denial.
Having discussed 'the several classes of Idols and their equipage', Bacon concludes that they must all
'be renounced and put away . . . and the understanding thoroughly freed and cleansed; the entrance into the Kingdom of Man, founded on the sciences, being not much other than the entrance into the Kingdom of Heaven, wherein none may enter except as a little child'.
Bacon's attack on Idols was timely and influential, and its effectiveness derived partly from the obvious validity of what he was saying and partly from the memorable and striking nature of the terms he used. However, he comes close to creating Idols himself, for the classification is rather arbitrary and can be confusing because its lines of demarcation are not clear. Our example of the fallacies which arose when the Greek imagined that he saw a centaur is not greatly illuminated if an effort is made to distribute them into Bacon's categories.