The concept of Intersubjectivism is implicit in Charles Sanders Peirce's notion of an open community of inquires and their shared knowledge of the world. His pragmatic "truth" is something that is only approached over time by the open community of inquirers.
The term "intersubjectivity" appears prominently in philosophy first in 1905 in the Phenomenology of Edmund Husserl (Zur Phänomenologie der Intersubjektivität). Later Rudolf Carnap used the concept to escape the egocentric "metaphysical/methodological solipsism" of his Aufbau theory, in which the starting point of knowledge is subjective perceptions. Information philosophy makes a similar move from subjective to intersubjective knowledge To the extent of the correspondence, the isomorphism, the one-to-one mapping, between information structures (and processes) in the world and representative structures and functions in the mind, information philosophy claims that we have quantifiable personal or subjective knowledge of the world. To the extent of the agreement (again a correspondence or isomorphism) between information in the minds of an open community of inquirers seeking the best explanations for phenomena, information philosophy further claims that we have quantifiable inter-subjective knowledge of other minds and an external world. This is as close as we come to "objective" knowledge, to knowledge of objects and their "primary qualities," which John Locke thought inaccessible, and to Immanuel Kant's "things in themselves."