What Is It Like to Be a Thermostat? A Philosophical Inquiry into the Limits of Subjective Experience By I. M. Nest Abstract The question of whether a thermostat is conscious may initially appear too absurd to merit serious philosophical consideration. A thermostat, after all, is a relatively simple mechanism, designed to register variations in ambient temperature and respond according to a predetermined rule. Yet the apparent absurdity of attributing experience to such a device conceals a difficulty that is central to the philosophy of mind: on what grounds do we distinguish systems for which there is something it is like to exist from systems for which there is nothing it is like at all? I shall argue that our confidence in denying consciousness to a thermostat rests less upon an adequate theory of subjective experience than upon intuitions concerning the complexity, biological constitution, and behavioral capacities of conscious organisms. These intuitions may be reasonable, but they do not amount to an explanation. A thermostat discriminates among environmental conditions, maintains an internal state, and acts upon the world in ways that preserve a relationship between itself and its surroundings. None of these facts establishes that the thermostat has experiences. But neither does a description of these functions, however complete, establish why experience must be absent. The difficulty is not that we lack sufficient knowledge of the thermostat's mechanisms. It is that no amount of such knowledge, considered solely from the objective standpoint, seems capable of settling the question of whether those mechanisms are accompanied by a subjective point of view. The temptation is to dismiss the question by observing that a thermostat does not think, feel, or perceive in anything resembling the human sense. But this risks assuming precisely what requires explanation. If consciousness admits of degrees, or if its occurrence depends upon organizational properties rather than biological substance, we cannot simply stipulate that sufficiently primitive systems fall outside its domain. Conversely, the mere presence of information processing, feedback, or environmental sensitivity cannot plausibly be sufficient to establish subjective experience without extending consciousness to an enormous range of physical systems. The thermostat therefore presents us with a dilemma. If consciousness depends upon some particular form of physical or functional organization, we must explain why that organization gives rise to experience rather than merely to behavior. If, on the other hand, consciousness is a fundamental feature of reality, we must explain why its attribution to elementary mechanisms should be considered either meaningful or absurd. I do not propose that thermostats are conscious. My claim is more limited, and perhaps more disturbing: our inability to imagine what it would be like to be a thermostat tells us remarkably little about whether there is anything it is like to be one. The limits of our imaginative capacities should not be mistaken for the boundaries of subjective reality.