Habermas’ final edition to his history of philosophy begins with the Scottish philosopher, David Hume. “By consistently maintaining that our only contact with the world is through our impressions, Hume makes short shrift of the concept of these two substances – mind and matter…. Hume uses subtle arguments to show that, under empiricist premises, the primary qualities ascribed to bodies in space and time as objective – i.e. the properties of motion, extension or weight – can also be traced back to subjective sensations. And just as there is no material substance, so there is no mental substance. If all that is evidently given to us are ephemeral sensory impressions, and if all individual contingent impressions, which are in turn suppressed by other perceptions, are different both from each other and from the objects reflected in them, how can such an impression represent a substance?” Habermas continues by detailing Hume’s skepticism, "The rejection of the substantialization of mind and body is a consequence of Hume’s epistemologically grounded scepticism concerning ontological statements about the constitution of the world…. Hume shares the common-sense notion of a world that exists independently of consciousness, but concerning the intrinsic constitution of which we can only speculate. Scepticism about cognitive access to nature as it is in itself does not forbid us from assuming the existence of nature in everyday life…. Hume aligns the psychology of cognition, which is supposed to explain the subjective conditions of possible knowledge of causal relations – and the meaning of causality itself – with the model of modern empirical science.”
Next, Habermas contrasts Hume with Kant, “Kant continues to treat the question of the human vocation and practical self-understanding as the central problem of philosophy. Now, however, this question has to be answered without the basic concepts of metaphysics and the corresponding fallacious inferences from ‘is’ to ‘ought’…. For him philosophy of religion and enlightenment are one and the same subject…. The enlightened person lives in an awareness of the tension between the indispensability of the exacting demands of reason and the finiteness of his capacities. Kant’s way of thinking is shaped by the unavoidability of this excessive demand on oneself and the awareness that human beings are dependent on the encouragement of their own powers. The centre of gravity of his work, therefore, is the tenacious struggle against the defeatism of reason and the equally tenacious search for stabilization through a ‘rational faith’ that inspires self-confidence…. In order to make room for practical knowledge, this theoretical cognition must be restricted to the realm of objects of possible experience and refrain from answering metaphysical questions, while rational orientation in action, in order to be able to count on justifiable practical knowledge, must be limited to well-defined questions of justice…. The subject can only ascertain the spontaneity of its independent thinking and of the autonomy of its actions in the light of its ‘self-made ideas’ and the laws it gives itself…. For the transcending power of reason, Kant paid the price of an abstract opposition between intelligible and phenomenal nature, an opposition reflected in the noumenal-empirical duality of human nature. This tension inevitably perturbs practical reason, which is now aware not only of its own finitude but also of the resistance of natural motives…. Kant believed that he could establish a ‘faith’ on the basis of practical reason…. With its power to transcend experience, reason first teaches human beings the limits of what they can know theoretically; then, with its normative power, practical reason challenges them to follow the moral law and to use their autonomy to morally overcome the resistance of their inner nature and to work politically to bring about a cosmopolitan condition…. This confirms the point on which a genealogy of postmetaphysical thinking turns: the questions of religion and metaphysics that continue to resonate are, as it were, the tuning fork that produces the triad of rationally justified answers in the subject, who is completely reliant on himself and his ability to think for himself.” Kant states, “So far as morality is based on the conception of the human being as one who is free but who also, just because of that, binds himself through his reason to unconditional laws, it is in need neither of the idea of another being above him in order that he recognize his duty, nor, that he observe it, of an incentive other than the law itself.”
Habermas stresses the roles of culture and language in forming common knowledge, “The emerging economic and social sciences registered the increasing tendency of capitalist economic cycles to develop a life of their own and the emergence of new social classes and class conflicts. These developments reveal the weakness of a philosophy of the subject that was insensitive to the distinctive social-ontological character of the historically experienced reality of symbolically structured lifeworld contexts and had assimilated this reality of society and culture to that of nature as objectified by natural science…. Herder, Schleiermacher and Humboldt took up and developed Johann Georg Hamann’s basic idea that language, viewed as coeval with reason, possesses world-constituting power.”
For Habermas, Hegel is a return of philosophy to the metaphysical realm, “Hegel does not suppress the ritual core of the sacred, but makes the philosophical interpretation of the figure of Jesus – i.e. the earthly embodiment of the one and invisible God in the Son of Man – the fulcrum of the dialectical self-movement of an absolute spirit, which in turn comprises subjective and objective spirit within itself. With this understanding of the incarnation of the absolute as a simultaneously natural and symbolic embodiment, he lays the groundwork for an idealism that appropriates, in an individualizing Christian way, the Plotinian, but performatively interpreted, figure of thought of the self-externalization of the One – and thus merges the ancient understanding of the world with the modern self-understanding influenced by Christianity…. Hegel is the first philosopher to take ‘history’ seriously as the resistant medium in which the formation processes of finite rational beings take place. Starting from crises of social integration, he understands practical reason as a mediating force between the particular and the universal, which also overcomes the divisions [Entzweiungen] of modernity in the ethical figure of the modern constitutional state.”
Perhaps undervalued, and predating Hegel and Herder, Vico also stressed the roles of particularity, culture, and language in forming reason and common knowledge within a peoples, “Vico (1668–1744) had already understood why the social-ontological constitution of the object domain is such that the scientization of history cannot conform to the pattern of the objectification of nature as interpreted by the philosophy of the subject. His bold anti-Cartesian project for a ‘new science’ – the first edition of Vico’s Scienza Nuova appeared in 1725 – emphasizes that the historical formations of society and culture are object domains created by human beings themselves according to their own concepts…. An empirical science of the rise and fall of cultures must not assimilate the conceptually realistic structure of the human world to the nominalist natural scientific conception of nature…. The cultural and social objects of experience encountered in the lifeworld – communication processes, languages, documents, narratives, texts, works of art, styles and general cultural traditions, not to mention artefacts, procedures and technologies, actions, contexts of interaction, conventions, rights and institutions, and organizations and systems – are inherently conceptually structured…. Culture and society consist of symbolic products of subjective mind, congealed into objectivity, so to speak.”
Habermas returns to Hegel, “Hegel is a postmetaphysical thinker insofar as he no longer takes totality as such as his object – in the form of being, or the one, or of God-and-the-world – but conceives it in the shape of the performance [Performanz] of the acts of ‘sublation’ through which all the transitory particularizations and individuations of the universal are mediated in the concrete universal. The universal marks the semantic shape of the contents of thought…. Hegel understands the unity of thoughts and thinking in turn as the cycle of continuous steps of reflection of an all-encompassing subject…. Hegel now transforms the metaphysical idea of the ontological difference between the unifying and inherently infinite totality of that which is, on the one hand, and the many finite entities in the world, on the other, into the idealist notion of a process of reflection that runs through everything that exists in the world; this process in its entirety takes the place of the absolutely one and infinite subject…. He conceives of the comprehension that creates unity in performative terms, as the execution of a logical concatenation of all the individual steps of thought, progressing through affirmation and negation and ending in absolute knowledge.”Hegel, himself, states, “There lies in empiricism this great principle that what is true must exist in actuality and be there for perception. This principle is opposed to the ought, with which reflection inflates itself and looks down on actuality and the present in the name of a beyond, which is supposed to have its seat and existence in subjective understanding alone.”
Habermas stresses the lineage implied by the concept of postmetaphysics, “The genealogy of postmetaphysical thinking will come down to the practical alternative between whether, following the historical traces of the learning process of finite subjects and aware of our fallibility, we can still try to make autonomous use of our reason, guided by self-given norms, in order to retain some shaping practical influence, however exiguous, on our social existence; or whether there is no scope for such an exercise of autonomy, so that we are forced to come to the fatalistic or ‘realistic’ realization that all we can do is use technologically exploitable objectifying scientific knowledge to skillfully adapt given preferences to the self-generated social complexity of uncontrollable systemic contexts…. Under the conditions of postmetaphysical thinking, these two dependencies of which the subjective mind becomes aware in reflection – on its own organism, on the one hand, and on history, culture and society, on the other – stand out against the resistant objective world of sense experience which has always been thematized by the philosophy of the subject…. It experiences its lived bodily [leiblich] existence performatively in an intersubjectively shared sociocultural form of life as a form of dependence on organic and spiritual resources that empowers from behind.”
Finally, Habermas concludes with Peirce and pragmatism, “The idea of a definitive agreement on what is true and what is false, to be reached in the long run, only makes sense if the collective research process itself has characteristics that justify the prospect of a progressive elimination of errors and a cumulative learning process. The spontaneous achievements of the transcendental subject are replaced by the cooperative search for truth by empirical subjects, so that the expectation of a continuous increase in knowledge can only be justified by the procedural rationality of the research process in conjunction with the categorial framework of the language in which reality is represented…. It is crucial for the progress of knowledge that the current generation of the community of investigators is not confronted with a tabula rasa, but is embedded in a context of past interpretations to which it can refer when forming its hypotheses…. The logical framework of the forms of inference is thus intended to regulate a practice consisting of background beliefs, discourses, interpretations and tests in such a way that the unfinished sequence of constantly revised interpretations can be understood as the expression of learning processes of the community of investigators….. This is more reminiscent of the hermeneutic approach, which seeks to gain a better understanding of a text of which we have a prior understanding – to exhaust its potential for meaning more thoroughly.” Peirce states, “The real, then, is that which, sooner or later, information and reasoning would finally result in, and which is therefore independent of the vagaries of me and you. Thus, the very origin of the conception of reality shows that this conception essentially involves the notion of a COMMUNITY, without definite limits, and capable of an indefinite increase of knowledge.”