Andy Mckilliam

Until recently, mental imagery has largely been regarded as an exclusively conscious phenomenon. However, recent empirical results suggest that mental imagery can also occur unconsciously. People who report having no experiences of mental imagery often perform similar to controls on behavioural tasks thought to require imagery. A surprising number of them also display significant levels of imagery-based priming, and recent neural decoding studies have shown that imagery-related information is being processed in their visual cortex. However, investigating unconscious imagery empirically is not straightforward. One challenge is to establish that imagery is genuinely unconscious as opposed to merely going unreported due to response biases. Another is to clarify how imagistic and indirect perceptual processing needs to be to qualify as imagery. In this paper, we take a closer look at the evidence for unconscious imagery, argue that it is not as compelling as it initially appears, and outline a strategy for advancing research on this question.

Philosophers of mind and philosophers of science have markedly different views on the relationship between explanation and understanding. Reflecting on these differences highlights two ways in which explaining consciousness might be uniquely difficult. First, scientific theories may fail to provide a psychologically satisfying sense of understanding—consciousness might still seem mysterious even after we develop a scientific theory of it. Second, our limited epistemic access to consciousness may make it difficult to adjudicate between competing theories. Of course, both challenges may apply. While the first has received extensive philosophical attention, in this paper I aim to draw greater attention to the second. In consciousness science, the two standard methods for advancing understanding—theory testing and refining measurement procedures through epistemic iteration—face serious challenges.

A central project for the neuroscience of consciousness is to reveal the neural basis of consciousness. For the past 20-odd years, this project has been conceptualized in terms of minimal sufficiency. Recently, a number of authors have suggested that the project is better conceived in mechanistic terms as the search for difference-makers. In this paper, I (i) motivate this mechanistic alternative to minimal sufficiency, (ii) develop it further by clarifying debates about the prospects of leveraging mutual manipulability to distinguish constitutive difference-makers from those that are merely causal, and (iii) explore the implications this has for recent debates concerning the status of the prefrontal cortex. I argue that adopting a mechanistic approach to the neuroscience of consciousness suggests that the prefrontal cortex is part of the neural mechanisms underlying consciousness even if it is not strictly speaking a necessary part.

Detecting introspective errors about consciousness presents challenges that are widely supposed to be difficult, if not impossible, to overcome. This is a problem for consciousness science because many central questions turn on when and to what extent we should trust subjects’ introspective reports. This has led some authors to suggest that we should abandon introspection as a source of evidence when constructing a science of consciousness. Others have concluded that central questions in consciousness science cannot be answered via empirical investigation. I argue that on closer inspection, the challenges associated with detecting introspective errors can be overcome. I demonstrate how natural kind reasoning—the iterative application of inference to the best explanation to home in on and leverage regularities in nature—can allow us to detect introspective errors even in difficult cases such as judgments about mental imagery, and I conclude that worries about intractable methodological challenges in consciousness science are misguided.

What should we make of systems that behave just like conscious creatures but operate via mechanisms that are profoundly different from our own? How should we even think about mechanistic similarity and difference in this context? To answer these questions, I take a closer look at the inferential machinery that allows us to justifiably draw conclusions about consciousness in others. I argue that inferences about consciousness in others are best viewed as involving analogical inferences grounded in explanatory considerations. I conclude that profound mechanistic difference severs the evidential link between behavioural evidence and subjective experience. I then draw on recent developments within the mechanistic philosophy of science to motivate a conception of mechanistic similarity that is not wedded to similarity of physical substrate and outline a strategy for resolving disputes about whether it is cognitive similarity or neural similarity that matters for inferences about consciousness.

It is often suggested that to make progress in consciousness science we need a theory of consciousness—one that tells us what consciousness is and what kinds of systems can have it. But this may be putting the cart before the horse. There are currently a wide range of very different theories all claiming to be theories of consciousness. How are we to decide between them if we do not already know which systems are conscious and what they are conscious of? In this paper I aim to do two things. First, I explain why a theory‐driven approach to consciousness science, even one sensitive to Lakatosian norms and updating in a Bayesian manner, may lead to divergence rather than convergence. Second, I draw on the history of thermometry and natural kind reasoning to sketch a theory‐neutral route towards progress in consciousness science.

The notion of a global state (or level) of consciousness is an increasingly important construct in the science of consciousness. However, exactly what a global state of consciousness is remains poorly understood. In this paper I offer an account of global states of consciousness as consciousness-related capacity modulations. On this view global states are not themselves phenomenal states – they are not occurring experiences. Rather, they are states that specify which of a creature’s overall consciousness-related capacities are currently online. Given that the search for the neural correlates of consciousness (NCC), as it is currently conceived, is the search for the neural basis of occurrent experiences, the NCC framework is incapable of revealing the neural basis of global states. As such, a mature science of consciousness will need to move beyond the search for NCCs, as that project is currently conceived.