Let that principle of some of the old philosophers, That all is Matter, and that there is nothing else, be received for certain and indubitable, and it will be easy to be seen by the writings of some that have revived it again in our days, what consequences it will lead us into.  Let any one, with Polemo, take the world; or with the Stoics, the aether, or the sun; or with Anaximenes, the air, to be God; and what a divinity, religion, and worship must we needs have!  Nothing can be so dangerous as principles thus taken up without questioning or examination; especially if they be such as concern morality, which influence men’s lives, and give a bias to all their actions.  Who might not justly expect another kind of life in Aristippus, who placed happiness in bodily pleasure; and in Antisthenes, who made virtue sufficient to felicity?  And he who, with Plato, shall place beatitude in the knowledge of God, will have his thoughts raised to other contemplations than those who look not beyond this spot of earth, and those perishing things which are to be had in it.  He that, with Archelaus, shall lay it down as a principle, that right and wrong, honest and dishonest, are defined only by laws, and not by nature, will have other measures of moral rectitude and gravity, than those who take it for granted that we are under obligations antecedent to all human constitutions.

5.  To do so is no certain Way to Truth.

If, therefore, those that pass for principles are not certain, (which we must have some way to know, that we may be able to distinguish them from those that are doubtful,) but are only made so to us by our blind assent, we are liable to be misled by them; and instead of being guided into truth, we shall, by principles, be only confirmed in mistake and error.

6.  But to compare clear, complete Ideas, under steady Names.

But since the knowledge of the certainty of principles, as well as of all other truths, depends only upon the perception we have of the agreement or disagreement of our ideas, the way to improve our knowledge is not, I am sure, blindly, and with an implicit faith, to receive and swallow principles; but is, I think, to get and fix in our minds clear, distinct, and complete ideas, as far as they are to be had, and annex to them proper and constant names.  And thus, perhaps, without any other principles, but barely considering those perfect ideas, and by comparing them one with another; finding their agreement and disagreement, and their several relations and habitudes; we shall get more true and clear knowledge by the conduct of this one rule, than by taking up principles, and thereby putting our minds into the disposal of others.

7.  The true Method of advancing Knowledge is by considering our abstract Ideas.