I personally read these as a description of the accepted methods and content of the learning of the time.
The originality, usefulness and necessity of his work in warning about these classes of errors has since been underappreciated. Bacon was known as the "father of empirical science" for his urging the use improved tools, measurements, observations and experiments rather than resting on ancient opinions and modern convention.
But it is always possible for any one at any time to fall into one of these classes of errors no matter how wonderful his methods are, and not only to fall into them, but to make of them a great virtue -- or "idol."
The deep fallacies of the mind, or general classes of errors into which the human mind is prone to fall, are arranged in the Novum Organon as the four idola:
The idola tribus, "idols of the tribe," are fallacies incident to humanity or the race in general. Of these, the most prominent are the proneness to suppose in nature greater order and regularity than there actually is; the tendency to support a preconceived opinion by affirmative instances, neglecting all negative or opposed cases; and the tendency to generalize from few observations or to give reality to mere abstractions, figments of the mind.
Manifold errors also result from the weakness of the senses, which affords scope for mere conjecture; from the influence exercised over the understanding by the will and passions; from the restless desire of the mind to penetrate to the ultimate principles of things.