Is there such a thing as consciousness without content? If so, is that minimal, empty consciousness, in fact, the constant ground underlying all conscious states? Thomas Metzinger launched an investigation of this question in the third Carnap lecture of a year ago; there’s a summary here (link updated to correct version) in a discussion paper, and a fully worked-up paper will appear next year (hat-tip to Tom Clark for drawing this to my attention). The current paper is exploratory in several respects. One possible result of identifying the hypothetical state of Minimal Phenomenal Experience (MPE) would be to facilitate the identification of neural correlates; Metzinger suggests we might look to the Ascending Reticular Arousal System (ARAS), but offers it only as a plausible place-holder which future research might set aside.

More philosophically, the existence of an underlying conscious state which doesn’t represent anything would be a fatal blow to the view that consciousness is essentially representational in character. On that widely-held view, a mental state that doesn’t feature representation cannot in fact be conscious at all, any more than text that contains no characters is really text. The alternative is to think that consciousness is more like a screen being turned on; we see only (let’s say) a blank white expanse, but the basic state, precondition to the appearance of images, is in place, and similarly MPE can be present without ‘showing us’ anything.

There’s a danger here of getting trapped in an essentially irrelevant argument about the difference between representing nothing and not representing anything, but I think it’s legitimate to preserve representationalism (as an option at least) merely by claiming that even a blank screen necessarily represents something, namely a white void. Metzinger prefers to suggest that the MPE represents “the hidden cause of the ARAS- signal”. That seems implausible to me, as it seems to involve the unlikely idea that we all have constantly in mind a hidden thing most of us have never heard of.

Metzinger does a creditable job of considering evidence from mystic experience as well as dreamless sleep. There is considerable support here for the view that when the mind is cleared, consciousness is not lost but purified. Metzinger rightly points to some difficulties with taking this testimony on board. One is the likelihood of what he calls “theory contamination”. Most contemplatives are deeply involved with mystic or scriptural traditions that already tell them what is to be expected. Second is the problem of pinning down a phenomenal experience with no content, which automatically renders it inexpressible or ineffable. Metzinger makes it clear that this is not any kind of magic or supra-scientific ineffability, just the practical methodological issue that there isn’t, as it were, anything to be said about non-existent content. Third we have an issue Metzinger calls “performative self-contradiction”. Reports of what you get when your mind is emptied make clear that the MPE is timeless, placeless, lacking sensory character, and so on. Metzinger is a little disgusted with this; if the experience was timeless, how do you know it happened last Tuesday between noon and ten past? People keep talking about brilliance and white light, which should not be present in a featureless experience!

Here I think he under-rates the power and indeed the necessity of metaphors. To describe lack of content we fall back on a metaphor of blindness, but to be in darkness might imply simple failure of the eyes, so we tend to go for our being blinded by powerful light and the vastness of space. It’s also possible that white is a default product of our neural systems, which when deprived of input are known to produce moire patterns and blobs of light from nowhere. Here we are undoubtedly getting into the classic problems that affect introspection; you cannot have a cleared mind and at the same time be mentally examining your own phenomenal experience. Metzinger aptly likens these problems to trying to check whether the light in the fridge goes off when the door is closed (I once had one that didn’t, incidentally; it gave itself away by getting warm and unhelpfully heating food placed near it). Those are real problems that have been discussed extensively, but I don’t think they need stop the investigation. In a nutshell, William James was right to say that introspection must be retrospection; we examine our experiences afterwards. This perhaps implies that memory must persist alongside MPE, but that seems OK to me. Without expressing it in quite these terms, Metzinger reaches broadly similar conclusions.

Metzinger is mainly concerned to build a minimal model of the basic MPE, and he comes up with six proposed constraints, giving him in effect not a single MPE state but a 6-dimensional space. The constraints are as follows.

• PC1: Wakefulness: the phenomenal quality of tonic alertness.

• PC2: Low complexity of reportable content: an absence of high-level symbolic mental content (i.e., conceptual or propositional thought or mind wandering), but also of perceptual, sensorimotor, of emotional content (as in full-absorption episodes).

• PC3: Self-luminosity: a phenomenal property of MPE typically described as “radiance”, “brilliance”, or the “clear light” of primordial awareness.

• PC4: Introspective availability: we can sometimes actively direct introspective attention

to MPE and we can distinguish possible states by the degree of actually ongoing access.

• PC5: Epistemicity; as MPE is an epistemic relation (“awareness-of”,) if MPE is successfully introspected, then we would predict a distinct phenomenal character of epistemicity or subjective confidence.

• PC6: Transparency/opacity: like all other phenomenal representations, MPE can vary along a spectrum of opacity and transparency.

At first I feared this was building too much on a foundation not yet well established, but against that Metzinger could fairly ask how he could consolidate without building; what we have is acknowledged to be a sketch for now; and in fact there’s nothing that looks obviously out of place to me.

For Metzinger this investigation of minimal experience follows on from earlier explorations of minimal self-awareness and minimal perspective; this might well be the most significant of the three, however. It opens the way to some testable hypotheses and, since it addresses “pure” consciousness offers a head-on attack route on the core problem of consciousness itself. Next year’s paper is surely going to be worth a look.