Status of knowledge

The school is firmly realist about knowledge: reason does not construct its object, it reaches the real order of things as it is in itself. The order and connection of ideas is the same as the order and connection of things, writes Spinoza, the true idea agreeing with what it represents. Descartes' clear and distinct ideas grasp the real essence of things, and the intelligible order of Leibniz's monads is the very architecture of reality: to know is to read the structure of the world, not to fabricate it.

Spinoza, Ethics, II, proposition 7 · Descartes, Meditations on First Philosophy, V · Leibniz, Monadology, §§ 56-62

If method is worth reforming, it is because there are, beneath the phenomena, real forms and laws to be discovered, not invented. The whole Baconian reform presupposes an ordered nature, independent of our mind, whose right knowledge fits its structure; knowledge is moreover measured by its operative power over things, the warrant that it has grasped the real and not a fiction of the mind.

Novum Organum, II, §1-4 (the doctrine of forms)

Newtonian confidence carries a realist thesis: the laws of nature are not convenient conventions but the real structure of an ordered world, which reason deciphers rather than constructs. To know is to lift the veil of prejudice and appearance and reach things as they are; error stems from ignorance and imposture, not from any relativity built into knowledge itself. This objectivism grounds the authority the Enlightenment grants to science over opinions and traditions.

d'Alembert, Preliminary Discourse to the Encyclopédie · Voltaire, Elements of Newton's Philosophy

Empiricism conceives of science as knowledge of observable regularities rather than of the inner nature of things: Locke holds the real essence of bodies to be beyond our reach and grants only a nominal essence, framed by the mind, to the kinds we sort things into. Berkeley, the third great figure of the school, radicalises this primacy of experience into idealism: for him esse est percipi, to be is to be perceived, and bodies are but collections of sensible ideas, which dismisses unintelligible matter without threatening the science of phenomena. The position leans toward a sober realism, anchored in experience, without claiming to grasp essences.

Locke, Essay Concerning Human Understanding, III, 6 and IV, 3 (real and nominal essence) · Berkeley, A Treatise Concerning the Principles of Human Knowledge, §3 and §9 (esse est percipi, against matter) · Hume, Enquiry Concerning Human Understanding, section IV

Locke distinguishes a thing's real essence (its inner constitution, unknown to us) from its nominal essence (the abstract idea we form from observable qualities, by which we sort it). Genera and species are thus partly the workmanship of the understanding; yet Locke holds to a mind-independent reality of bodies' primary qualities, which anchors his position toward a cautious realism rather than an avowed constructivism.

Essay Concerning Human Understanding, III, ch. 3 and ch. 6 (real and nominal essence) · Essay Concerning Human Understanding, II, ch. 8 (primary and secondary qualities)

No description grasps a reality endowed with inherent existence, since there is none: the categories and distinctions of knowledge belong to conventional truth, dependent and useful constructions, never the mirror of essences in themselves. Our statements order an empty (śūnyatā) world rather than reflecting independent structures: a pronounced epistemic constructivism, at the conventional level.

Mūlamadhyamakakārikā (Fundamental Verses on the Middle Way), XXIV, 8-10 (the two truths) · Vigrahavyāvartanī (The Dispeller of Disputes), on the means of knowledge (pramāṇa)

Inquiry, for Dewey, does not passively mirror a pre-existing object: it transforms an indeterminate situation into a determinate one, and so shapes its own objects of knowledge. Knowing is an active, instrumental construction, embedded in a practice, rather than the tracing of an independent reality. The leaning is constructivist, without denying that reality offers resistance.

Dewey, Logic: The Theory of Inquiry (1938) · Dewey, The Quest for Certainty (1929)

In De Motu, Berkeley anticipates scientific instrumentalism: the force, attraction and absolute space of Newton's mechanics are not hidden realities that physics would uncover but convenient terms, calculational fictions that let us predict and order phenomena. The physicist does not unveil real causes; he establishes rules of use among signs. This distrust of science's claim to describe a mind-independent structure of the world removes him from scientific realism, without amounting to a social constructivism: it is idealism that gives it its colour.

De Motu (On Motion), §§1-6 and 35-42

The same thing appears differently according to the animal perceiving it, the sense organ, the subject's state, distance, mixture, or custom: this is the observation that Aenesidemus' ten tropes catalogue and order. Yet to adjudicate these irreconcilable appearances and say which one delivers the real thing, one would need an absolute standpoint, outside every condition of appearance, which no one has. The trope therefore bites exactly where the dogmatist claims to describe natures in themselves: we never grasp anything but the relative, which reduces every assertion about essence to epochē.

Sextus Empiricus, Outlines of Pyrrhonism, I, 36-163 · Diogenes Laertius, Lives, IX, 79-88

The theory of ideology holds that the ruling ideas of an age are the ideas of its ruling class: consciousness is socially situated and tends to disguise the real relations. Knowledge is not a neutral contemplation but is shaped by class interests, which brings Marxism close to a social constructivism, without renouncing a truth unveiled by critique.

Marx and Engels, The German Ideology (1845-1846)

The fulcrum is intentionality, taken over from Brentano: all consciousness is consciousness of something, never a content sealed upon itself. It follows that the object cannot be severed from the act that aims at it: meaning and objectivity are not brute facts deposited in nature but are constituted in that relation. The target is objectivist naturalism, which takes the world for an in-itself independent of all consciousness and forgets that it has itself posited it. Husserl thus shows that scientific idealities are rooted in the lifeworld (Lebenswelt), forgotten as their ground; Merleau-Ponty recalls that science is a second-order expression of the perceived world. The stance leans toward constructivism, without sliding into relativism.

Husserl, The Crisis of European Sciences and Transcendental Phenomenology (1936) · Merleau-Ponty, Phenomenology of Perception (1945), preface