Concept

Idealism

Intro

Idealism is the position that the basic stuff of reality is mental, not material. The world is made of minds and ideas; matter is either a kind of dream, a presentation in a cosmic mind, or an appearance rather than an underlying reality. It is the opposite of materialism (which says everything is made of matter).

The most famous version is George Berkeley's, in the early 1700s. Berkeley argued that "to be is to be perceived." The tree in the quad is real because God is always perceiving it; if no one were perceiving it, it would not exist. Material substance, the idea of stuff that exists independent of any mind, Berkeley argued was incoherent and unnecessary. Samuel Johnson kicked a stone and said "I refute him thus"; Berkeley would have said the kick is itself a mental event in a mental quad.

Other versions: Plato's Forms (the truest reality is the realm of pure intelligible forms, not the changing material world), Hegel's Absolute Idealism (history is the unfolding of one cosmic Mind coming to know itself), and modern philosophical theist views like Bernardo Kastrup's analytic idealism (everything is in one universal consciousness).

Christianity's relationship to idealism is mixed. Mainstream Christian metaphysics (Augustine, Aquinas, the Reformed tradition) is realist: the world is real, distinct, external, created by God but genuinely other than Him. A small theological-idealist strand (Jonathan Edwards, Gordon Clark) holds the world is continuously thought into being by God, so it is mental all the way down but in His mind, not ours.

Both Christian options reject materialism. They differ on whether matter is real-but-derived or just-an-appearance-in-God's-mind. The interesting modern revival of idealism among scientists and philosophers (in response to the consciousness problem) gives Christianity a friendlier neighbor than materialism, even if mainstream Christian metaphysics does not go fully idealist.

In full

Idealism is the metaphysical view that reality is fundamentally mental, constituted by ideas, minds, or thought, rather than material. It is the historical foil to Materialism and distinct from Naturalism (some idealists are theists, others are not). Christian engagement with idealism is mixed: some strands (Jonathan Edwards, B. B. Warfield in places, Gordon Clark) embrace a theological idealism in which the world is sustained by God's continuous thought; mainstream Christian metaphysics (Aquinas, Augustine, the Reformed tradition broadly) affirms realism, the world is created by God but exists as a real, distinct, external reality.

Definition / core claim

The core idealist claim: the most fundamental kind of thing that exists is mental. Material objects either depend on minds for their existence (subjective idealism), are constituted by mental content in a cosmic mind (objective / theological idealism), or are appearances rather than things-in-themselves (transcendental idealism).

Three theses commonly bundled with idealism:

Mind is metaphysically prior to matter, minds are not reducible to brains; matter (if real) is reducible to or dependent on mind.
Esse est percipi (Berkeley), to be is to be perceived; unperceived matter is incoherent.
The intelligibility of reality is grounded in its mental character, the cosmos is comprehensible because it is thought-like.

Historical development

Plato (Republic, Timaeus, c. 380-360 BC), the Forms are the most real entities; sensory things are shadows. Often called the proto-idealist position.
Plotinus and Neoplatonism (3rd c. AD), emanationist hierarchy from the One through Intellect to Soul to Matter.
George Berkeley (A Treatise concerning the Principles of Human Knowledge, 1710; Three Dialogues between Hylas and Philonous, 1713), subjective idealism. Material substance is incoherent; physical objects are bundles of perceptions sustained by God's continuous perceiving.
Immanuel Kant (Critique of Pure Reason, 1781), transcendental idealism. Space, time, and the categories are forms of intuition / understanding the mind imposes on a noumenal reality we cannot directly access.
G. W. F. Hegel (Phenomenology of Spirit, 1807; Science of Logic, 1812-16), objective / absolute idealism. Reality is the dialectical self-unfolding of Absolute Spirit (Geist). History is the realization of reason.
Jonathan Edwards (Notes on the Mind, c. 1720s; "Of Atoms", c. 1722), theological idealism. Physical reality exists as God's continuous communication / thought. Bodies are divine acts of will sustaining ordered sense-experience.
F. H. Bradley, J. M. E. McTaggart, Josiah Royce (late 19th / early 20th c.), British and American absolute idealism. Reality as a single mental whole.
Gordon Clark (mid-20th c.), Reformed Scripturalist idealism: knowledge and reality reside in God; physical particulars are derivative.
Bernardo Kastrup (The Idea of the World, 2019; Why Materialism is Baloney, 2014), contemporary analytic idealism, framed against materialism.

Variants

Subjective idealism (Berkeley)

To be is to be perceived. Material substance is a meaningless abstraction; what we call "physical objects" are coherent patterns of sense-experience. God is the universal perceiver whose continuous perception sustains the world's existence even when no human is observing it.

Transcendental idealism (Kant)

We cannot know things-in-themselves. The structure of experience (space, time, causality) is contributed by the perceiving mind, not read off the noumenal world. This is a more epistemic than metaphysical idealism.

Objective / absolute idealism (Hegel, Bradley)

Reality is mental, but not in any individual's mind. The cosmos is the unfolding of Absolute Spirit / Mind / Reason. History, nature, and morality are moments in this unfolding.

Theological idealism (Edwards, Clark, some Reformed)

Physical reality is sustained by God's continuous thought / will. The world is real, but its reality is constituted by divine mental act, not by independent matter. Distinct from pantheism: God is not identical to creation; creation is a sustained divine thought / communication.

Panpsychism / cosmopsychism

A neighboring family: consciousness is fundamental and ubiquitous (panpsychism) or there is one cosmic consciousness in which everything participates (cosmopsychism). Galen Strawson, Philip Goff, Bernardo Kastrup are contemporary defenders.

Christian engagement

ris3n's note scores theological idealism at 42/100 biblical alignment versus realism at 90/100, with the principal problems being:

Genesis 1:1 describes God creating an external "heavens and the earth", language of making, not of thinking-into-being.
John 1:3, "all things came into being through Him", names a real ontological coming-into-being, not a mental projection.
Romans 8:19-22, creation groans for redemption, suggesting a real subject distinct from God.
The Incarnation requires real flesh; if matter is illusion, the body of Christ becomes problematic (Docetic tendency).
Evil becomes either part of God's mental content or unreal, both tear at biblical theism.

The cross-examination in develops these points in courtroom format, arguing that objective idealism either collapses into pantheism, makes God the author of evil, or empties the gospel of its physical reality.

That said, aspects of idealism are theologically useful:

God's sustaining of creation (Colossians 1:17, Hebrews 1:3), "in him all things hold together".
The Logos doctrine (John 1:1), creation through the divine Word / Reason.
The intelligibility of nature reflecting God's rationality.

These are realist-with-idealist-flavor: God's ongoing thought sustains reality, but reality is genuinely external to him.

Strengths and weaknesses

Strengths:

Honors the apparent priority of mind, consciousness, and intelligibility.
Avoids the hard problem of consciousness by starting from mind.
Coherent with the Christian sense that reality is meaning- saturated and divinely upheld.
Subjective idealism actually motivates Berkeley's critique of scientific materialism, physical-object talk needs a perceiver to be coherent.

Weaknesses:

Subjective idealism collapses into solipsism if God's role as cosmic perceiver is rejected.
Objective / absolute idealism collapses into pantheism (see Pantheism), Hegel especially.
Cannot make natural sense of the gritty externality of experience: stubbed toes, persistence of unobserved objects, the testimony of physical science.
Theological idealism risks confusing God's knowledge of things with their being, eroding the Creator/creature distinction (see Ipsum Esse Subsistens).
The doctrines of incarnation, resurrection, and bodily redemption sit awkwardly in any view that denies real materiality.