Au 18ème siècle, la pensée s'intéresse à elle-même : connaître ses propres actes, diriger son propre cours. La soif intellectuelle ne se porte pas seulement vers le monde, mais vers elle-même. Une force la pousse à revenir à son origine, à s'intéresser à son mode d'action. C'est en ce sens que se pose le problème du progrès : il ne s'agit pas seulement d'une extension constante du savoir, mais d'un retour conscient à son centre. Toutes les énergies restent liées à un moteur commun : la raison.

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Texte publié par Alexander Pope en 1734.

Know then thyself, presume not God to scan;

The proper study of Mankind is Man.

Plac'd on this isthmus of a middle state,

A being darkly wise, and rudely great:

With too much knowledge for the Sceptic side,

With too much weakness for the Stoic's pride,

He hangs between; in doubt to act, or rest,

In doubt to deem himself a God, or Beast;

In doubt his Mind or Body to prefer,

Born but to die, and reas'ning but to err;

Alike in ignorance, his reason such,

Whether he thinks too little, or too much:

Chaos of Thought and Passion, all confus'd;

Still by himself abus'd, or disabus'd;

Created half to rise, and half to fall;

Great lord of all things, yet a prey to all;

Sole judge of Truth, in endless error hurl'd:

The glory, jest, and riddle of the world!

Go, wond'rous creature! mount where Science guides

Go, measure earth, weigh air, and state the tides;

Instruct the planets in what orbs to run,

Correct old Time, and regulate the Sun;

Go, soar with Plato to th'empyreal sphere,

To the first good, first perfect, and first fair;

Or tread the mazy round his follow'rs trod,

And quitting sense call imitating God;

As Eastern priests in giddy circles run,

And turn their heads to imitate the Sun.

Go, teach Eternal Wisdom how to rule -

Then drop into thyself, and be a fool!

Superior being, when of late they saw

A mortal man unfold all Nature's law,

Admir'd such wisdom in an earthly shape,

And shew'd a NEWTON as we shew an Ape.

Could he, whose rules the rapid Comet bind,

Describe or fix one movement of his Mind?

Who saw its fires here rise, and there descend,

Explain his own beginning, or his end?

Alas what wonder! Man's superior part

Uncheck'd may rise, and climb from art to art:

But when his own great work is but begun,

What Reason weaves, by Passion is undone.

Trace Science then, with Modesty thy guide;

First strip off all her equipage of Pride,

Deduct what is but Vanity, or Dress,

Or Learning's Luxury, or Idleness;

Or tricks to shew the stretch of human brain,

Mere curious pleasure, ingenious pain:

Expunge the whole, or lop th' excrescent parts

Of all, our Vices have created Arts:

Then see how little the remaining sum,

Which serv'd the past, and must the times to come!

On ne peut étudier un homme sans étudier l'humanité dans son ensemble.