In Three Dialogues between Hylas and Philonous, in Opposition to Skeptics and Atheists, Berkeley formed a famous argument against the existence of matter. However, the main purpose of his argument was not to refute Locke, but to show the necessity of God.

Philonous Good morning, Hylas: I did not expect to find you abroad so early.

Hylas It is indeed something unusual; but my thoughts were so taken up with a subject I was discoursing of last night, that finding I could not sleep, I resolved to rise and take a turn in the garden.

Philonous It happened well, to let you see what innocent and agreeable pleasures you lose every morning. Can there be a pleasanter time of day, or a more delightful season of the year? that purple sky, those wild but sweet notes of birds, the fragrant bloom upon the trees and flowers, the gentle influence of the rising sun, these and a thousand nameless beauties of nature inspire the soul with secret transports; its faculties too being at this time fresh and lively are fit for these meditations, which the solitude of the garden and tranquility of the morning naturally dispose us to. But I am afraid I interrupt your thoughts: for you seemed very intent on something.

Berkeley, who is about to use Philonous to prove that there is more absurdity in maintaining that there is material, or in philosophical terms an underlying substance or substratum behind the things we sense, than maintaining there isn't, has, with this soliloquy established beyond doubt that Philonous does indeed experience the same things as everyone else.

Hylas It is true, I was, and shall be obliged to you if you will permit me to go on in the same vein: not that I would by any means deprive myself of your company, for my thoughts always flow more evenly in conversation with a friend, than when I am alone: but my request is this, that you would suffer me to impart my reflections to you.

Philonous With all my heart, it is what I should have requested myself if you had not prevented me.

Hylas I was considering the odd fate of those men who have in all ages, through an affection of being distinguished from the vulgar, or some unaccountable turn of thought, pretended either to believe nothing at all or to believe the most extravagant things in the world. This however might be borne, if their paradoxes and skepticism did not draw after them some consequences of general disadvantage to mankind. But the mischief lieth here; that when men of less leisure see them who are supposed to spent their whole time in the pursuits of knowledge professing an entire ignorance of all things, or advancing such notions as are repugnant to plain and commonly received principles, they will be tempted to entertain suspicions concerning the most important truths, which they had hitherto held sacred and unquestionable.

Philonous I entirely agree with you, as to the ill tendency of the affected doubts of some philosophers, and fantastical conceits of others, I am even so far gone of late in this way of thinking, that I have quitted several of the sublime notions I had got in their schools for vulgar opinions. And I give it to you on my word, since this revolt from metaphysical notions, to the plain dictates of nature and common sense, I find my understanding strangely enlightened, so that I can now easily comprehend a great many things which were before all mystery and riddle.

The major thrust of philosophical inquiry during the seventeenth century was a revolt against both mature Scholasticism and the more modern rationalism. These systems of thought required involved technical arguments. These arguments usually revolved around the meaning of technical terms invented by the philosophers themselves and thus had little meaning for the average person. From Bacon on, particularly in England, the tendency was toward the use of terms that anyone could understand.

Hylas I am glad to find that there was nothing in the accounts I heard of you.

Philonous Pray, what were those?

Hylas You were represented in last night's conversation, as one who maintained the most extravagant opinion that ever entered into the mind of man, to wit, that there is no such thing as material substance in the world.

Philonous That there is no such thing as what Philosophers call material substance, I am seriously persuaded: but, if I were made to see anything absurd or skeptical in this, I should then have the same reason to renounce this that I imagine I have now to reject the contrary opinion.

Hylas What, can anything be more fantastical, more repugnant to common sense, or a more manifest piece of skepticism, than to believe there is no such thing as matter?

Philonous Softly, good Hylas. What if it should prove, that you, who hold there is, are, by virtue of that opinion, a greater skeptic and hold more paradoxes and repugnance to common sense, than I who believe no such thing?

Hylas You may as soon persuade me, the part is greater than the whole, as that, in order to avoid absurdity and skepticism, I should ever be obliged to give up my opinion in this point.

Philonous Well, then you are content to admit that opinion for true, which upon examination, shall appear most agreeable to common sense, and remote from skepticism?

Hylas With all my heart. Since you are for raising disputes about the plainest things in nature, I am content for once to hear what you have to say.

Philonous Pray Hylas, what do you mean by a skeptic?

Hylas I mean what all men mean, one that doubts everything.

Philonous He, then, who entertains no doubt concerning some particular point, with regard to that point cannot be thought a skeptic.

Hylas I agree with you.

Philonous Whether doth doubting consist in embracing the affirmative or negative side of a question?

Hylas In neither; for whoever understands English cannot but know that doubting signifies a suspense between both.

Philonous He then that denieth any point, can no more said to doubt of it than he who affirmeth it with the same degree of assurance.

Hylas True.

Philonous And, consequently, for such his denial is no more to be esteemed a skeptic than the other.

Hylas I acknowledge it.

Philonous How cometh it to pass, then, Hylas, that you pronounce me a skeptic because I deny what you confirm, to wit, the existence of matter? Since, for aught you can tell, I am as peremptory in my denial as you are in your affirmation.

Hylas Hold, Philonous, I have been a little out in my definition; but every false step a man takes in discourse is not to be insisted on. I said indeed that a skeptic was one who doubted of everything; but I should have added, or who denies the reality and truth of things.

Philonous What things? Do you mean the principles and theories of the sciences? But these you know are universal intellectual notions, and consequently independent of matter; the denial therefore of this doth not imply the denying of them.

Hylas I grant it. But are there no other things? what think you of distrusting the senses, of denying the real existence of sensible things, or pretending to know nothing to them. Is this not sufficient to denominate a man a skeptic?

Philonous Shall we therefore examine which of us it is that denies the reality of sensible things, of professes the greatest ignorance of them; since, if I take you rightly, he is to be esteemed the greatest skeptic?

Hylas That is what I desire.

Philonous What mean you by sensible things?

Hylas those things which are perceived by the senses. Can you imagine that I mean anything else?

Philonous Pardon me, Hylas, If I am desirous clearly to apprehend your notions, since this may much shorten our enquiry. Suffer me to ask you this further question. Are those things only perceived by the senses which are perceived immediately? Or, may those things properly said to be sensible which are perceived mediately, or not without the intervention of others?

Hylas I do not sufficiently understand you.

Philonous In reading a book, what I immediately perceive are the letters, but mediately, or by means of these, are suggested to my mind the notions of God, Virtue, Truth, &c. Now, that the letters are truly sensible things, or perceived by the sense there is no doubt; but I would know whether you take the things suggested by them to be so too.

Hylas No, certainly; it were absurd to think God, or Virtue sensible things, though they may be signified and suggested to the mind by sensible marks, with which they have an arbitrary connection.

Philonous It seems then, that by sensible things you mean those only which can be perceived immediately by sense.

Hylas Right.

Philonous Doth it not follow from this that though I see one part of the sky red, and another blue, and that my reason doth evidently conclude there must be some cause of that diversity of colors, yet that cause cannot be said to be a sensible thing, or perceived by the sense of seeing?

Hylas It doth.

Philonous In like manner, though i hear variety of sounds, yet i cannot be said to hear the causes of those sounds?

Hylas You cannot.

Philonous And when by my touch I perceive a thing to be hot and heavy, I cannot say, with any truth or propriety, that I feel the cause of its heat or weight?

Hylas To prevent any more questions of this kind, I tell you once and for all that by sensible things I mean those only which are perceived by the sense, and that in truth the senses perceive nothing that they do not perceive immediately: for they make no inferences. the deducing therefore of causes or occasions from effects and appearances, which alone are perceived by sense, entirely relates to reason.

Philonous This point then is agreed between us--that sensible things are those only which are perceived by sense. You will further inform me , whether we immediately perceive by sight anything beside light, and colors and figures; or by hearing anything but sounds; by the palate, anything beside tastes; by the smell beside odors; or by the touch, more than tangible qualities.

Hylas We do not.

Philonous It seems, therefore, that if you take away all sensible qualities, there remains nothing sensible?

Hylas I grant it.

Philonous Sensible things therefore are nothing but so many sensible qualities. or combinations of sensible qualities.

Hylas Certainly.

Philonous Heat is then a sensible thing?

Hylas Certainly.

Philonous Doth the reality of sensible things consist in being perceived? or, is it something distinct from their being perceived, and that bears no relation to the mind?

Hylas To exist is one thing, and to be perceived is another.

Philonous I speak with regard to sensible things only; and of these I ask, by their real existence you mean a subsistence exterior to the mind and distinct from their being perceived?

Hylas I mean a real absolute being, distinct from and without any relation to their being perceived.

Philonous Heat therefore, if it be allowed a real being, must exist without the mind?

Hylas It must.

Philonous Tell me, Hylas, is this real existence equally compatible to all degrees of heat, which we perceive; or is there any reason why we should attribute it to some and deny it to others? and if there be pray let me know that reason.

Hylas Whatever degree of heat we perceive by sense, we may be sure the same exists in the object that occasions it.

Philonous What! the greatest as well as the least?

Hylas I tell you the reason is plainly the same in respect of both: they are both perceived by the sense; nay the greater degree of heat is more sensibly perceived; and consequently, if there is any difference, we are more certain of its real existence than we can be of the reality of the lesser degree.

Philonous But is not the most vehement and intense degree heat a very great pain?

Hylas No one can deny it.

Philonous And is any unperceiving thing capable of pain or pleasure?

Hylas No certainly.

Philonous Is your material substance a senseless being or a being endowed with sense and perception?

Hylas It is senseless without doubt.

Philonous It cannot therefore be the subject of pain.

Hylas By no means.

Philonous Nor consequently of the greatest heat perceived by sense, since you acknowledge this to be no small pain?

Hylas I grant it.

Philonous What shall we say then of your external object; is it a material substance or no?

Hylas It is a material substance with sensible qualities inhering in it.

Philonous How then can heat exist in it, since you own it cannot in a material substance? I desire you would clear this point.

The undeniable consequence of this line of reasoning is that sensible qualities cannot exist in material objects. They can only exist in a perceiving being, a mind. Bishop Berkeley had a very good reason for making this claim. According to Locke's empiricism, we can know nothing about anything except through its sensible qualities. Thus, despite his deep religious convictions Locke has developed a way of knowing the world around us that is completely devoid of God. But if, as Berkeley has pointed out, the sensible qualities through which we obtain our knowledge of the world around us cannot exist in anything material. And at the same time we obviously sense objects around us, there must be something else that causes these sensations to be there for us to perceive. Many Christian philosophers including some Scholastics and some Rationalists taught that God was not only the creator of the world but he was responsible as well for the continued existence of the world. In order that we can all experience the same things in the same way, and in order that things did not pop out of existence every time no one was around to perceive them, Berkelian idealism required a constant mind. This was the major purpose of Berkeley's philosophy, to show that in spite of Locke's empiricism, God was still necessary for the world to persist.

John Locke was the father of empiricism. He was also the spiritual father of that period we call the "enlightenment." In Europe many idealized England for its love of freedom and religious tolerance. However, they were dismayed by the results of this freedom. Leopold Mozart, father of the composer, brought the young Wolfgang to London, but he refused to remain in spite of tempting offers because, as he put it, "I will not bring up my children in such a dangerous place."

What began as a peculiarly English aberration struck a nerve when it crossed the channel and began what is referred to as the "Enlightenment." Unfortunately the term as it is generally used implies much more continuity than actually occurred. First, and most universally, it represents a rejection of rationalism, or the idea that knowledge can be derived purely through reasoning. In France, the birthplace of rationalism, the attitude toward rationalism turned particularly vitriolic. Voltaire's Candide is a satirical denunciation of Leibniz' "Best of all possible worlds." Paris was the home of the "Philosophes". these were philosophers who followed in the Baconian tradition of celebrating the accomplishments of science. Particularly Dennis Diderot, who was the most instrumental of the group in producing the first "Encyclopedia", or compendium of all scientific knowledge.

But there was another side to this rejection of rationalism, and this tended toward an rejection of science and reason along with it. While this attitude had greater repercussion later, it played a strong part in eighteenth century thought as well. In his First Discourse, Rousseau, in the outspoken manner of his day, called for a return to simplicity, to the "noble savage".

The mind has its needs as does the body. The needs of the body are the foundations of society, those of the mind make it pleasant. While government and laws provide for the safety and well-being of assembled men, the sciences, letters, and arts, less despotic and perhaps more powerful, spread garlands of flowers over the iron chains with which men are burdened, stifle in them the sense of that original liberty for which they seemed to have been born, make them love their slavery, and turn them into what is called civilized peoples. Need raised thrones; the sciences and arts have strengthened them. Earthly powers. love talents and protect those what cultivate them. Civilized peoples, cultivate talents: happy slaves, you owe to them that delicate and refined taste on which you pride yourselves; that softness of character and urbanity of customs which make relations among you so amiable and easy;; in a word, the semblance of all the virtues without the possession of any.

We will have much more to say about Rousseau later, but I would like to impress on you that this attitude against rationality also was construed as a revolt against pretension. The philosopher who did most in the eighteenth century to dispel the fog of pretension implied in the language of philosophy was David Hume.