In the Logische Aufbau der Welt, Rudolf Carnap was concerned with the objectivity of science, and how his rational reconstruction, could successfully explain why science is objective, despite starting with an autopsychological basis. In section 66, Carnap raises the challenge his system must solve: How can science consist of “intersubjective valid assertions,” (Logische, p. 106) when all physical objects are constructed from subjective experience?
In other words, how can we clear the dividing bar between subjectivity and objectivity, and leap from the quicksand of inconstant, subjective experience to the solid ground of valid and objective truths in science? If every physical object is constructed from the contents of subjective experiences, then how can science even claim objective status? Could science be reduced to nothing but the “relations” (Logische, p. 106) between the ever-changing, always inaccessible private experiences of the individual? Given that each private experience of every individual are all fundamentally different from one another, then how can any scientific statement ever truly be objective?
Carnap was familiar with the traditional problems of philosophy, and knew that the leap from the private experiences of individuals to objective knowledge that these same individuals could agree on was very difficult, but he was confident that his program of rational reconstruction could provide the solution.
Carnap’s solution was pretty simple: although the “material” (Logische, p. 107) of private experiences are all different, for they cannot be truly compared, there are “structural properties” (Logische, p. 107) that are “analogous” for all private experiences. In other words, Carnap asserted that all private experiences had corresponding structures, for they were not isolated islands of subjectivity floating in the sea of infinite space. Therefore, science, in order to be objective, must be only about those structural properties.
Moreover, Carnap said that in order to be objective, science is a series of statements about structures, because all objects of knowledge are about form, not content, and they’re represented as “structural entities.” (Logische, p. 107) I suppose that the form of experience must be a perceptual structure or a category that is distinguished by a common characteristic, whereas the content of experience is that which is contained, the thing or things included within the form.
These “structural properties” must be the form of the “material” of private experience, as opposed to its content. The material or content of experience may be wholly incompatible, always changing and forever inaccessible, yet they contain common structural elements, and science describes these structures. Given that such structures are “analogous” for all experiences, and science represents them, science achieves objectivity. Thus, science is much more than the mere relations of experience.
The Logical Structure of the World, Rudolf Carnap, tr. By Rolf. A. George, University of California Press, Berkeley/Los Angeles 1967