In these pages we will be concerned with sensations themselves (that is, with concrete sensory events) and also with certain of the characteristics that sensations exemplify. Although we will consider characteristics of other kinds as well, we will be primarily concerned with characteristics that are qualitative. Qualitative characteristics include being a pain and being an itch. They also include the sensory characteristic that is exemplified by the gustatory sensations one has when one tastes orange juice, and the sensory characteristic that is exemplified by the olfactory sensations one has when one smells gasoline.

A terminological point. Ordinary language does not contain many names for qualitative characteristics of sensations (or qualia, as I shall sometimes call them). In addition to “being a pain” there is “being an itch” and “being a case of pleasure.” But there are not many others. In most cases we pick out qualitative characteristics of sensations by resorting to descriptions, and this is what I have done in giving the last two examples in the first paragraph. However, it can seem that descriptions like “the sensory characteristic that is exemplified by the gustatory sensations one has when one tastes orange juice” suffer from crippling ambiguities. If, for example, one tastes orange juice right after brushing one's teeth with mint flavored toothpaste, one experiences a sensation – a most unpleasant sensation – that is quite different than the one that is normally associated with tasting orange juice.