Here is another paragraph that I think represents the main idea of the book.

"It may not be an easy matter to obtain an experimental result that constitutes a confirmed predicted schematic asymmetry even in a single-researcher-informant experiment. But it is, ultimately, the replication of a confirmed predicted schematic asymmetry in a multiple-non-researcher-informant experiment that makes us confident about the validity of our hypotheses that have given rise to the predicted schematic asymmetry. It is also such replication that would prompt us to pay serious attention to the empirical and "factual" claims put forth by others dealing with a language about which we do not have native intuitions. One may in fact suggest that it is the replication of a confirmed predicted schematic asymmetry in multiple-non-researcher-informant experiments that would make us hopeful that language faculty science as an exact science may indeed be possible."

Roughly speaking, a predicted schematic asymmetry is a prediction deduced by our hypotheses. We say that we have obtained a confirmed predicted schematic asymmetry if we have obtained experimental results in accordance with the predicted schematic asymmetry.

The above remark should be understood with the clear understanding of the point made in:

"Taking the internalist approach to language, we consider the obtaining of a confirmed predicted schematic asymmetry in a single-researcher-informant experiment as the first step toward establishing a fact in language faculty science as an exact science. A confirmed predicted schematic asymmetry is based on a predicted schematic asymmetry. Predicted schematic asymmetries are given rise to by universal hypotheses, along with language-particular hypotheses and bridging hypotheses. It is in this sense that an individual informant's judgment is revealing about universal properties of the language faculty. It is also in this sense that facts in language faculty science as an exact science are closely related to our hypotheses about universal properties of the steady state of the language faculty."