Sir Isaac Newton's
For the Use of the LADIES.

IN Six Dialogues

From the Italian of Sig. Algarotti.

Volume I.

Quæ legat ipsa Lycoris. Virg. Ec. x.


Printed for E. Cave, at St. John's-Gate,


Mons. de Fontenelle

If you addressed your ingenious and entertaining Dialogues to the illustrious Dead, who had first given you the Idea of that Work, and therefore thought yourself obliged to seek your Hero even in the Obscurity of the Tomb; how much greater Reason have I to dedicate these Discourses to one of the most illustrious among the Living, whom I am indebted to for the Example which first set me upon composing them, and who has given me so perfect a Model of polite Wit and agreeable Writing?


Your Plurality of Worlds first softened the savage Nature of Philosophy, and called in from the solitary Closets and Libraries of the Learned, to introduce it into the Circles and Toilets of Ladies. You first interpreted to the most amiable Part of the Universe those Hieroglyphics, which were at first only for Initiates; and found a happy Method to imbellish and intersperse with the most beautiful Flowers a Field, which once seemed incapable of producing any Thing but the most rugged Thorns and perplexing Difficulties. You may be said to have committed the Care of revolving the Heavens to Venus, and the Graces, instead of those Intelligences to whom Ignorance had anciently assigned that Office.


The Success was answerable to the Beauty and Novelty of the Undertaking. That half of our World, which always commands the Votes of the other, has given its Approbation to your Book, and in the most agreeable manner consecrated it to Posterity.

May I venture to flatter myself, that my Light and Colours will have the same Fate as your Worlds? If a Desire of pleasing those who afford us so much Pleasure, were sufficient to make its Fortune, I should have nothing to envy you. But I am too sensible of the very many Defects that attend my Performance, Defects that I cannot help lamenting; for not to say any Thing of your Talents, and that happy Art of rendering every Thing you undertake entertaining and agreeable, the Plu <iv> rality of Worlds, which you have chose for your Subject, seems of all others to present the most pleasing and elegant Images, and is therefore the most agreeable to your Dialogists, that the vast Field of Philosophy could ever supply you with. It presents to the Mind nothing less than the Stars and Planets, the grandest and most shining Objects of the Universe. There are but few of the subtile Enquiries of Science, into which you are obliged to enter. The Arguments, upon which your Opinion is founded, do not carry such a Certainty in them, as to make the Conversation grow languid.

I have endeavoured to set Truth, accompanied with all that is necessary to demonstrate it, in a pleasing <v> Light, and to render it agreeable to that Sex, which had rather perceive than understand. Light and Colours are the Subject of my Dialogues; a Subject, which, however lively and agreeable it may seem, is not in itself either so pleasing or so extensive as your Worlds. I am obliged to descend to many difficult and minute Particularities of Knowledge; and my Arguments are unhappily incontestable. Experiments, which must be explained with the greatest Accuracy imagineable. It was indeed just, that the Ladies, who by your Work had been made acquainted with the great Change introduced by Des Cartes into the thinking world, should not be ignorant of the new, and 'tis probable the last Change, of which the illustrious Sir Isaac Newton was the Author. But it was extremely difficult to recivilize <vi> this savage Philosophy, which in the Paths of Calculation and the most abstruse Geometry was returning more than ever to its ancient Austerity. You have embellished the Cartesian Philosophy; and I have endeavoured to soften the Newtonian, and render its very Severities agreeable.

However, the abstruse Points, upon which I have been obliged to treat, were only such as are absolutely necessary, and always interspersed with something that may relieve the Mind from that Attention which they require. In the most delightful Walk we are sometimes glad to find a verdant Turf to repose ourselves upon. Lines and mathematical Figures are entirely excluded, as they would have given these Discourses too Scientific an <vii> Air, and appeared formidable to those, who to be instructed must be pleased. Mathematical Terms are as much as possible avoided; and if ever any do occur, they are explained by the Assistance of the most familiar Objects. The Difficulties raised against any particular Experiment, the History of optical Inventions, metaphysical Doubts, and the various Opinions of different Philosophers, preserve the Subject from that continued Uniformity, which would make it disagreeable and tedious. I have endeavoured as much as possible to render it lively, and make my Readers interest themselves in it as they would in a Composition for the Theatre. Is there any Thing (especially where Ladies are concerned) in which a Writer should omit any Endeavours to move the Heart?


The marvellous, of which the Heart always desirous of being affected is so fond, happily arises in true Philosophy of itself, without the help of Machines. I have made a sort of Change or Catastrophe in the Philosophy of my Marchioness, who is at first a Cartesian, afterwards a Proselyte to Malebranche, and at last obliged to embrace the System of that Person, who ought to be placed at the Head of his Species, if Superiority and rank among Mankind were determined by Strength of Genius and the most comprehensive Knowledge. This great Philosopher's general System of Attraction is not omitted, because it has a natural Connexion with the particular Attraction observed betwixt Bodies and Light. Thus these Dialogues may be considered as a com <ix> plete Treatise of the Newtonian Philosophy. The Sanctuary of the Temple will always be reserved for the Priests and Favourites of the Deity; but the Entrance and its other less retired Parts will be open to the profane.

The Style I have endeavoured to follow is what I believed most proper for Dialogue, clear, concise, interrupted, or interspersed with Images and Turns of Wit. I have taken the utmost Care to avoid those perplexed and long Periods closed by the Verb, which only serve to run the Reader out of Breath, and are besides repugnant to good Sense, and much less agreeable to the Genius of our Language than is generally believed, and certainly cannot be agree <x> able to the Genius of those, who write with an Intention of being understood. I have left them entirely to those, who forsake the[1] Saggiatore for the[2] Fiammetta, together with those antique and obsolete Words which constitute so great a Part both of their Knowledge and Delight. The Count di Castiglione, in his Courtier, two Centuries ago, ventured to write in such a Manner, as to be understood by his Contemporaries, and throwing aside the Affectation of Gothic Terms, adapted his manner of writing to the Forms of Speech in Use among the polite and well bred Persons of his Time. Custom, the sovereign Judge in all Languages, (except perhaps our own) was <xi> his Guide; and thus he enriched us with the finest Piece (as far as regards the Style) which the Italian Language has to boast of. For what Reason should I think myself obliged to make use of the antiquated Discourses of some clamorous Haranguer of four hundred Years standing, as a Model for a Work of Philosophy and Politeness; and rather than talk to Ladies in the Language of the present Age, address my Discourse to the Devotees of the thirteenth Century?

This minute Dissertation I thought in some Measure due to yourself, to let you see how little I have neglected in a manner of Writing, which may be regarded as your own. Nor was it less due to my Countrymen, since <xii> this Work, whatever it be, is written in their original Language. Young Mathematicians, in giving the solution of a Problem, generally describe the Steps by which they investigated it: It is only those of an established Reputation who are permitted to give the simple Solution, and leave to others the Care of finding by what Means they attained it.

I would not however appear to set a greater Value upon this Work than perhaps the World will think it deserves, or suppose myself to have given a perfect Solution of this Problem. I am too well acquainted both with myself, and the Difficulty of the Enterprize, to entertain so high an Opinion of the Performance. I have perhaps only <xiii> seen the Method, which ought to be followed, and yet have not followed it myself. Raphael and Guercino had nearly an equal Knowledge of the Preparations necessary for the right Designing of a Figure, and yet were extremely unequal in the Execution of it.

Whatever may be the Success of my Undertaking, the Ladies, for whom this Work is principally intended, ought at least to think themselves obliged to me, if I have procured them a new kind of Amusement, which others may perhaps carry to a greater Degree of Perfection; and if I have brought into Italy a new Mode of cultivating the Mind, rather than the present momentary Fashion of adjusting their Head-dress and placing <xiv> their Curls. Travellers should be the Importers of Wit, and of those reciprocal Advantages, which different Nations even in this respect have over each other. Happy the Society formed upon the Italian Fancy, the French Politeness, and British good Sense!

We ought to think ourselves obliged to your Nation, and yourself in particular, for giving us an Example to render common and easy what was once mysterious and difficult, and to write in our own Language what by a superstitious Veneration was appropriated to the Latin, and at the same Time perplexed with Greek, that most formidable Weapon of Pedantry. We may in this respect cast the same Reproach on the Italians as <xv> Mr. Pope does in another Case on the English in his fine Prologue to Cato.

Our Scene precariously subsists too long

On French Translation and Italian Song,

Dare to have Sense yourselves, assert the Stage,

Be justly warm'd with your own native Rage.

If we except some Translations from the French, there is nothing among us but Songs and Collections of Verses, which every Day overspread us like a Deluge, and are the Torments of our Age. In the modern Books, written in the Italian Language, the Ladies can find nothing but Sonnets full of a metaphysical Love, which I suppose must affect them as little as the anti- <xvi> quated Expressions of superannuated Cicisbei. Let the Age of Realities once more arise among us, and Knowledge instead of giving a rude and savage Turn to the Mind, and exciting endless Disputes and wrangling upon some obsolete Phrase, serve to polish and adorn Society. I have at least opened the Way to something, which is neither Grammar not Sonnet; and I shall flatter myself to have done much more, if what the Ladies inspired me with, has the good Fortune to meet with your Approbation.



The First Dialogue.

INtroduction; a general Idea of Physics, and an Explanation of the most remarkable Hypotheses concerning Light and Colours. Page I

The Second Dialogue.

That Qualities, such as Light, Colours, and the like, are not really in Bodies. Metaphysical Doubts concerning our Sensations of them. Explication of the general Principles of Optics. p. 76

The Third Dialogue.

Several Particulars relating to Vision, Discoveries in Optics, and a Confutation of the Cartesian System.

p. 148


The Third Dialogue.

Several Particulars relating to Vision, Discoveries in Optics, and a Confutation of the Cartesian System.

p. 148

Errata in Volume I.

PAGE 26. L. 15. for Spread, read overspread. p. 40 l. 16. for below, r. below; p. 46. l. 9. for examine, r. prosecute. p. 103. l. 12. for Appearances, r. Appearances? p. 106. l. 18, 19. for which were capable, r. capable. p. 131. l. 16 for, that is r. that is, p. 150. l. 11. for of r. to. p. 178. l. 18. for given, r. given? p. 182. l. 22. for Ounce, r. Inch. p. 219. l. 26, for I, an, r. I. An.

[1] An Epistle from Galileo to Virginius Cæsarinus, in which the Author gives a very elegant Exposition of his System of Physics and Astronomy.

[2] A Romance, by Boccace

© 2017 The Newton Project

Professor Rob Iliffe
Director, AHRC Newton Papers Project

Scott Mandelbrote,
Fellow & Perne librarian, Peterhouse, Cambridge

Faculty of History, George Street, Oxford, OX1 2RL -

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