In everyday life, we employ two different kinds of explanation: appeals to causes and appeals to reasons. Reason explanations are invoked in those areas where understanding requires the apprehension of a rational relation between explanans and explanandum. For this to be possible, it seems that the explanans and the explanandum must both, in some sense, involve intentional content. So, for example, I might explain Hermione’s strange hopping behavior by saying that she wants to get water out of her ear, and believes that she can accomplish this by hopping. This explanation is satisfying because it provides a characterization of the behavior – “ear-draining” – that is rationally connected to the content of Hermione’s beliefs and desires.
In the case of causal explanations, there is no question of there being any rational relation between cause and effect. I fell asleep because I took an antihistamine. It doesn’t matter to the adequacy of the explanation how I thought of my action, nor does it matter what my intention was in taking the pill. The substance I ingested it simply has the effect of putting me to sleep, as a matter of natural law.
What do we say, however, in a case where we seem to have a causal interaction between two events, one of which possesses, and the other of which lacks, intentional content? What I have in mind is the process by which perception produces empirical beliefs. We know that visual perception begins with light striking the retina, and that it ends (in a typical case) with a true empirical belief. The belief state has intentional content, a content that we want to say is justified or warranted by the perceptual event that caused it. But the event of light’s striking the retina is not a contentful state – it is simply a stage in a physical causal process, and not the right type of state to rationally justify anything.
In my paper, I will propose a model of rational justification that will explain how this gap between causes and reasons can be bridged – providing, as it were, a new mode of understanding. I argue that although the physical state of the retina at the beginning of the perceptual process does not possess intentional content, it does possess something else: informational content. Informational content is always physically encoded. My suggestion is that, if the processing mechanisms that transform the retinal image into a contentful mental state are physically sensitive to those physical parameters of the retinal surface that encode information that is rationally relevant to the content of that downstream mental state, then we have a principled basis for saying that the mental state is, in the epistemic sense, based on the state of the retina. Thus we have a transaction between environment and mind that is simultaneously causal and rational.