Is the Cosmos All There Is? A Critique of Naturalism

Carl Sagan once claimed, “The cosmos is all that is or was or ever will be.” This is not a statement of fact but a statement of belief.

A Statement Beyond Proof

First, Sagan did not (and arguably could not) prove this claim. It functions as an assertion rather than a testable conclusion. The authority of a scientist does not transform a philosophical claim into an empirical fact; what is asserted without evidence can be set aside without evidence.

Second, how could one know that “the cosmos is all that is”? To make such a claim, one would already need access to “all that is,” which is precisely what is in question. Even within physics, the introduction of multiverse models complicates the idea of a single, exhaustive cosmos.

Third, if one was not present from the beginning, how could one know that the cosmos is all that “was”? There is no experiment, observation, or testimony that could establish such a total claim about the past.

Fourth, without the ability to predict the future with certainty, there is no way to justify the claim that the cosmos is all that “ever will be.” At best, this is extrapolation; at worst, it is speculation.

Naturalism as Worldview

What underlies Sagan’s statement is not science itself, but a philosophical commitment—often called naturalism or materialism. This is a worldview: a framework of assumptions that shapes how one interprets reality.

Naturalism holds that the natural world is all that exists. As such, it is not a scientific conclusion but a starting premise. Scientific theories, by contrast, are specific hypotheses tested through observation and experiment. No conceivable experiment could verify the claim that “the cosmos is all that is or was or ever will be,” because the claim is not empirically bounded.

Closely related terms include:

• Materialism: the doctrine that nothing exists except matter and its movements.

• Naturalism: the view that everything arises from natural causes, excluding the supernatural.

• Physicalism: the thesis that everything is ultimately physical.

Though distinct in nuance, each position denies any reality beyond the physical or natural domain.

The Problem of Consciousness

The central difficulty for naturalism is consciousness. There is one thing we can be certain of: that consciousness exists. As Descartes argued, “I think, therefore I am.” Even doubt confirms the presence of a doubter.

Yet consciousness resists straightforward explanation in physical terms. Despite extensive research, there is no widely accepted account of how subjective experience arises from brain processes. At most, we observe correlation—not causation—between neural activity and conscious awareness.

Philosopher Thomas Nagel sharpened this issue by noting that a conscious organism is one for which there is “something it is like” to be that organism. This subjective dimension does not easily reduce to computation or physical description.

It is also useful to distinguish cognition from consciousness. Cognition can be understood as information processing—something like computation. Consciousness, however, involves lived experience, the felt quality of awareness itself.

Reversing the Assumption

Rather than assuming that matter produces mind, one could invert the relationship: mind or consciousness may be fundamental, with the physical world emerging from it.

Some interpretations of quantum theory gesture in this direction. As Rosenblum and Kuttner note in Quantum Enigma, quantum mechanics challenges the idea of a fully observer-independent physical reality. The tension between physics and consciousness has persisted since the early development of quantum theory.

From this perspective, consciousness is not a byproduct of matter but the condition for the appearance of matter. In contemplative practices such as mindfulness meditation, one may directly observe that awareness is distinct from thought and more fundamental than it.

Beyond Naturalism

If consciousness is the one indubitable reality, then a worldview that excludes it—or attempts to reduce it entirely to physical processes—appears incomplete.

This does not necessarily entail a strict dualism of mind and matter. An alternative is to view reality as a single underlying whole with two aspects: an inner, experiential dimension (consciousness) and an outer, observable dimension (the physical). David Bohm’s distinction between implicate and explicate orders offers one way of conceptualizing this relationship.

There is no decisive evidence that the physical universe exhausts all that exists. That conclusion often rests not on proof, but on prior assumption. If something non-physical exists, it may not resemble physical objects at all—and thus may not be detectable by the same methods.

Consciousness, then, becomes central. It is not only the hardest problem for naturalism; it may be the key to a more complete account of reality.