Roger Bacon

There are four chief obstacles to grasping truth: authority, habit, popular opinion, and the concealment of ignorance.

Experimental science is the mistress of all speculative sciences.

Reasoning draws a conclusion, but does not make the conclusion certain.

All science requires mathematics.

The strongest arguments prove nothing so long as the conclusions are not verified by experience.

He who knows not mathematics cannot know any other sciences.

Theories are of no use if they cannot be tested by experiment.

The secrets of nature are not revealed to those who rely on books alone.

Without experiment, nothing can be sufficiently known.

For in the books of the Gentiles, and of the Saracens, and of all unbelievers, there is much that is useful for the understanding of the Scriptures, and for the government of the world, and for the correction of morals, as well as for the sciences.

The greater part of the world is ignorant of the true wisdom, and is ruled by error and deception.

The four greatest stumbling blocks to understanding are: authority, long-standing custom, the sense of the ignorant crowd, and the hiding of one's own ignorance under the show of wisdom.

For without experiment nothing can be sufficiently known. Therefore, he who wishes to be certain of the truths of things must have recourse to experiment.

It is impossible for the human mind to attain to the perfect truth in anything, unless it be aided by the grace of God.

Theology itself, which is the queen of the sciences, cannot be perfect without philosophy.

The study of languages is therefore necessary for all sciences, and especially for theology.

The mathematical sciences are the gate and the key to the understanding of all other sciences.

Ignorance is the mother of all errors.

For the infidels possess many excellent things, and much wisdom, from which we Christians can derive profit.

The multitude of students is very great, and the multitude of books is infinite, but the true knowledge is very rare.