Objectivity is not coextensive with science but it does associate with one or another of the epistemic virtues that scientists strive after in the course of their work. Nor is it an atomic concept, the authors claim. There are several aspects to objectivity, each of which have had stronger emphasis than the others at various times. The authors argue that objectivity is a fusion of several notions that occurred in the 19th century with a revival of the subject/object distinction in Kantian philosophy.
The book traces this history through that of atlases, those published manuscripts of deliberate observation intended to be comprehensive references of their subject. This is appropriate for several reasons. One reason is that there is a very clear publishing record of atlases in biology, botany, crystallography, and other natural sciences. Many of these books still exist. Second is the ancillary record, also still well preserved, of the authors' own account of their methodology and its justification. We have good data about what atlas authors believed to be the proper way to represent their subject. Third, it is obvious that the atlas is meant to be the crystallized product of observation. Whatever else objectivity might mean, it is rooted in observation, and to observe what is present for the purpose of representation (with the emphasis on re-presentation -- to present again) must, in some significant sense, capture what is essential to the object represented.
This history of the atlas goes through phases corresponding to the aforementioned aspects of scientific objectivity. Truth-to-nature came be a virtue of objective representation earliest. Though this did not mean to represent accurately. Rather, it was considered more virtuous to represent the species, even when this meant picking and choosing the most beautiful parts among many specimens and representing a composite that would stand in for the ideal of its kind. An ideal which was never--and perhaps would never be found in any single specimen. This task may have been made easier by the fact that photography would not exist for another century. The artists could blend their specimens according to criteria that had less to do with technical accuracy than with an individual sense of aesthetics.
The above is anathema to our modern sense of objectivity. Questions about whether atlas representations were unduly influenced by their authors' theoretical biases lead to heated debates, even at the time. So truth-to-nature gave way to mechanism, the substitution of fallible human judgment for dispassionate, instrumental copying. When photography entered the scene it became both the symbol for--and preferred instrument of the new epistemic virtue. The invention of new instrumental aids for observation went hand in hand with the new belief that the observer should not introduce themselves into the act. Will-to-will-lessness became a virtue of the working scientist as the self came to be seen more as an intrusion on the proper representation of things. Since the pursuit of truth has the avoidance of error as its companion, this suppression of one's individuality, along with all its own subjective inclinations, came to be the paragon of objectivity in 20th century science. It happened to coincide with a positivist philosophy which pushed for universalism in how science was communicated. It also coincided with the actual emergence of a global community of working scientists.
And this is probably what the general public thinks of as objectivity today. Yet among working scientists this uninvolved and blind copying of nature began to show its limitations as well. One may emphasize the importance of representing what the object is in itself, but eventually one questions whether there is any "in itself" to be found. Observation of an object is not without an observer. And knowledge of what things are, like all forms of knowing, must be knowledge for us and conform to our own specific capacities for receiving it. The emphasis shifts from science as theory to engineering, where things are less about "being" and more about "doing" (How do we make it work?) This is where the purpose of representation is to instruct. And at this point the "re" of "representation" is dropped and what remains is a presentation, that ephemeral performance before an audience that is seen once and exists no more. This is theater over cinema. The atlas image exists for training the eye of the acolyte. No longer does the working scientist labor to make the perfect carbon copy of nature. Instead they create emphasis to highlight important features. Training the judgment of a brain surgeon to recognize the signs of tumors may require more than natural images of actual cases. At first they may require guidance in seeing what the expert notes at a glance. Once the acolyte becomes the expert, these training images can be abandoned.