But now it is surely obvious that this whole wealth of theory cannot be extracted from any single occasion of sense-experience.
Sellars does not of course deny that sense-experience plays a part in our knowledge of the physical world; the part it plays, however, is first and foremost causal.
In other words, in using language we seem to bring something to our perceptions of sense-experience which is not directly present in the experience itself.
Another criticism levelled at Russell's view is that it makes an important but questionable assumption about the basic nature of sense-experience.
Secondly, it is easy to show that our ordinary judgements of perception assert more than is vouchsafed by the sense-experiences from which they issue.
Before Descartes, philosophers held that human beings were endowed with both sense and intellect, and that sense-experience brought the intellect into contact with the substances that were the topics of science.
In the experience of certain art objects, he suggests, the "intimacy" that is implicit in human sense-experience becomes more or less explicit.
But why should Reason, as opposed to sense-experience, be the arbiter of knowledge?
Other modes of sense-experience, e.g. hearing and smelling, will be dealt with only incidentally.
If meaning was closely connected with sense-experiences, it was hard to see what experiences could confirm or disconfirm the existence of a God.
Things in the world seem to affect one another causally in ways that are difficult to account for properly by mere reports of sense-experiences.
The mind was thus dependent for its scientific knowledge on sense-experience.
The World opens with several chapters of criticism of the common-sense view of material things - criticism of the view of the physical world that comes naturally to us, and that is based on sense-experience.