Subjective idealism
Explanation
The Irish bishop and philosopher George Berkeley pushed the empiricism of his day to an astonishing conclusion: matter, understood as a substance independent of mind, does not exist. His famous formula esse est percipi (to be is to be perceived), set out in his Treatise (1710), inverts common sense: instead of minds perceiving a pre-existing material world, there are perceptions whose only reality consists in being experienced.
The argument starts from an analysis of what a table, an apple or any physical object really is. When we examine it, what we find are colours, shapes, hardnesses, smells: in short, ideas in a mind. We never have access to a supposed matter lying behind those ideas. If the only evidence of the world is conscious perceptions, positing an additional material substance is an unnecessary and, what is more, contradictory hypothesis.
An obvious question arises: if objects exist only while someone perceives them, does the tree in the garden cease to exist when we all close our eyes? Berkeley answers with a theological twist: there is an infinite mind, God, who continuously perceives the whole of creation and thereby gives it continuity. Objects are ideas in the divine mind that we partially grasp.
Berkeleyan idealism does not deny the reality of the everyday world: apples remain sweet, stones remain hard and bruise us if we trip over them. What it denies is that this reality consists of anything other than perceptual content itself. Consciousness is not a window onto an external world, but the very fabric of which what we call the world is made.
This position influenced figures as diverse as David Hume, Arthur Schopenhauer and twentieth-century phenomenology. More recently, Bernardo Kastrup's analytic idealism has revived the Berkeleyan intuition in the language of contemporary science, holding that consciousness is ontologically fundamental and that matter is a representation within it.
The standard objections are well known: it seems counterintuitive, it multiplies the functions attributed to God, and it smacks of anthropocentrism (why should the qualities the human mind happens to experience be the primary ones?). But the challenge it poses is genuine: how do we justify the existence of a matter that, by definition, lies beyond any possible experience?
Strengths
- Parsimonious ontology: a single (mental) substance instead of two.
- Dissolves the hard problem: if everything is mental, there is no gap between the physical and the experiential.
- Anticipates by two centuries contemporary debates on the primacy of information.
- Coherent with first-person experience as primordial datum.
Main critiques
- Its dependence on God to guarantee the regularity of the world is seen as ad hoc by secular philosophy.
- Difficulty in accounting for intersubjectivity: how do different minds coordinate on the same object?
- Risk of solipsism if the role of the divine observer is weakened.
- According to Kantian critics, it confuses epistemic conditions with ontological ones.