The content of consciousness is made up out of multiple fields of inner and outer senses, relative to the body, as well as ideational fields such as memory, expectation, imagination and temporality. You might say that they are overlapping fields, but this would be to simplify the relations between them, implying that there are marginal regions where they manifestly coincide. Certainly they seem to be joined together, but this might more accurately resemble a patchwork with hidden gaps and seams. The natural presumption is that the synthetic unity of the subject is paramount and justifies the unity of awareness, but there is no obvious witnessing of this. The witnessing is rather an individual feature of each diverse field, an attribute of consciousness as such. The intuitive certainty of a unified self is a posterior construction or interpretation layered over the the individual components in a process of rapid alternation. If this seems a rather Buddhistic insight, the fact remains that there is no especial care whose focus is the unity of the subject, it is at best a parsimonious working hypothesis.