Rene Descartes
A portrait of René Descartes by Sébastien Bourdon.

What’s really out there, in the external world? This question, in various forms, has resurfaced in philosophy time and time again.

In our minds we are aware of things via sense data—their colours, their shapes, how they feel, and so forth. But do we know what’s really there? For our minds might tell an incorrect or partial story.

In the 17th century a great debate emerged. Rationalists (Descartes, Spinoza, Leibniz) argued it was our capacity of reason that gave us knowledge of reality or a lack thereof. Empiricists (Locke, Berkeley, Hume) argued that knowledge was grounded in sensory experience. Who was right?

Let’s take a look at some of the hottest takes.

Thomas Hobbes (b. 1588): We represent objects in our minds. Their ‘appearances’ are caused by physical processes which are not themselves perceived. Still, since Hobbes thought objects, in origin, do exist, he was a realist.

René Descartes (b. 1596): Like Hobbes, Descartes (pictured) rejected the view that mental representations share form with real objects. What we sense could be the tricks of an evil demon or a deceiving god. This made Descartes a sceptic who, nonetheless, argued that we do know we exist in virtue of our critical, doubtful minds: ‘Cogito, ergo sum’ (‘I think, therefore I am’).

John Locke (b. 1632): Dispositions give us natural tendencies but the mind is a blank slate at birth. Experience grants the materials of knowledge through ‘ideas of sensation’ (similar to Hume’s impressions). However, it would be unintelligible to say we can secure knowledge about properties in objects: our minds only detect mind-dependent qualities (e.g. colour). Locke, therefore, was an ‘indirect realist’ since he thought we had secondary access to the external world. ‘‘Tis evident, the Mind knows not Things immediately, but only by the intervention of the Ideas it has of them’ (An Essay Concerning Human Understanding).

George Berkeley (b. 1685): Berkeley believed in the power of perception to understand the nature of reality. However, believing realism (direct or indirect) to be false, he claimed that all qualities are housed in the mind, whereby God is the only cause. Each of us is a perceiver or perceived: ‘esse est percipii (aut percipere)’ (‘to be is to be perceived (or to perceive)’) (Principles and Dialogues). To truly understand the world, then, is to understand the mind of God, contrary to the mechanical science of Newton et al. Thus Berkeley was an idealist, according to which a world existing unperceived is incomprehensible.

Martin Heidegger (b. 1889): Fast-forward to the 20th century—Heidegger offered a phenomenological account of reality which is arguably realist. Heidegger claimed that only in phenomena do things really show themselves. There are appearances, things that become known via other things (e.g. an infection through an itch). There are also seemings, things which are not as themselves thanks to private modifications of phenomena (e.g. a road looking longer than it is). But phenomena can also express ‘being-in-the-world’—or ‘being-with-things’—via non-representational encounters with ‘innerworldly’ things, founded in skilful engagements which aren’t necessarily mentally experienced. For example, this could be a practical relation with a hammer, whose being is manifested in my capacity for utilising it. Through phenomena we maintain real relations with things which appear out of themselves.

Where’s your vote going?