Nineteenth-century philosophy

3. The turn against idealism: materialism, positivism, empiricism, naturalism

After the authority of Hegelian idealism was questioned from the 1840s onwards, the remainder of the century is marked by a battle between those who sought to go back to the eighteenth century and re-think the doctrines of Locke, Hume, Bentham or the French materialists, and those who believed that this was a retrograde step, which could only lead to the same mistakes and with them a threat to freedom, reason, morality and religion.

Perhaps the most obvious sense in which the second half of the nineteenth century saw a return to the eighteenth was in the way that the major movements of the period - materialism, positivism, empiricism - went back to a conception of science and of science’s relation to philosophy that belonged to the seventeenth and eighteenth centuries, when the scientific revolution had decisively shaped philosophical thinking (see Science, 19th century philosophy of). It would be wrong to characterize the German idealism of the first half of the nineteenth century as crudely ‘anti-scientific’; nonetheless, it did see itself as opposed to the scientific paradigms of the seventeenth and eighteenth centuries, particularly Newtonianism. In the early nineteenth century, the new approach of Naturphilosophie, espoused primarily by Schelling, Goethe and Hegel, in fact became the favoured scientific outlook with some researchers, and bore real fruit in the work of Lorenz Oken, Hans Christian Ørsted, and Johann Wilhelm Ritter, amongst others; but in the second half of the nineteenth century, this idealist Naturphilosophie was viewed as mere metaphysical speculation, divorced from true science, which was once again seen as requiring a commitment to the mechanistic paradigms of explanation which the Naturphilosophen had sought to question. Thus, in relation to the natural sciences in the second half of the nineteenth century, philosophy can be seen as returning to positions it had adopted previously, when under the influence of the scientific revolution in the seventeenth and eighteenth centuries.

In the eighteenth century, one way in which that influence was most directly felt was in the conception philosophers came to have of the ultimate nature of reality, as physicalistic, mechanistic, and deterministic. This view was adopted by the radical philosophes of the Enlightenment, particularly Julien de La Mettrie and Paul d’Holbach, who were uncompromising in their scientific materialism. While aiming to overcome the Cartesian dualism of mind and matter, they also (and much more broadly) saw the material world in essentially mechanistic terms. They also used the authority and methods of science to challenge all metaphysical speculation and apriorism, and instead defended a thoroughgoing empiricism. Likewise, materialism in the nineteenth century came to adopt a similar view, taking this to be the lesson of contemporary science, which they saw as continuous with seventeenth- and eighteenth-century physicalism. The thinking of La Mettrie and d’Holbach thus has its nineteenth-century counterpart in the work of Carl Vogt, Jacob Moleschott, Ludwig Büchner and Heinrich Czolbe in Germany; John Tyndall in Britain; and Nikolai Chernyshevskii in Russia (see also Nihilism; Russian §2; Russian Materialism: ‘the 1860s’). The impact of Darwin and Darwinism also played a vital role in underlining the authority of this broadly materialist and naturalistic outlook, and extending it to the understanding of the processes of history (see Materialism §3).

While materialism represents perhaps the most direct influence of science on philosophy, a less direct influence can be found in the revival of empiricism and the related position of positivism, where philosophers looked to science and scientific methods to understand how knowledge of the world is acquired, what form that knowledge takes and how far it can extend. As in the seventeenth and eighteenth centuries, this view rested on a sense that scientific inquiry was hugely successful, and so must form a model for all our cognitive endeavours. This model was inductivist: using observations and generalizations based on observations, science is able to uncover the law-governed causal relations between natural phenomena. According to this view, we are thereby able to reach an adequate understanding of the world, in the sense of an understanding that is perfectly satisfactory to science, without engaging in metaphysical speculation or attempting to transcend the boundaries of experience; no further kind of knowledge is possible for us, or even desirable, insofar as empirical science provides us with a fully adequate understanding of the world around us. As Mill makes clear, in adopting this sort of position, the empiricists and positivists of the nineteenth century saw themselves as returning to the earlier empiricist tradition of the seventeenth and eighteenth centuries:

We have here a characteristic mix of empiricist and positivist themes, built around a renewed faith in the methods and results of science as these were conceived of in the seventeenth and eighteenth centuries, together with a sharp awareness of the limits of scientific inquiry from a metaphysical perspective: metaphysical questions concerning the ‘hidden causes of the phenomena’ must be left unanswered, but in a way that leaves the adequacy of our investigations untouched. The sharp distinction between metaphysics and science that emerged in the seventeenth and eighteenth centuries can be seen to mark the positivism and empiricism of the second half of the nineteenth century, where in both periods, the distinction was used to prioritise science over metaphysics, whereas in the early part of the century, the order of priority had been the opposite. (See Ardigo, R.; Avenarius, R.; Brentano, F.C.; Cattaneo, C.; Comte, A.; Italy, philosophy in §2; Lewes, G.H.; Mach. E.; Martineau, H.; Poland, philosophy in §3; Positivism in the social sciences; Positivism, Russian; Positivist thought in Latin America; Twardowski, K.)

A third respect in which science came to influence philosophy from the 1840s onwards, in a manner that paralleled the influence it possessed in the seventeenth and eighteenth centuries, was the way in which respect for science (particularly physiology and psychology) led to a naturalistic view of the mind, as operating in accordance with processes and laws occurring in the natural causal order, with no place for any Kantian ‘transcendental subject’ outside this order. This has implications both for philosophy of mind, and for epistemology, where the issue is to show how various mental capacities and forms of knowledge (such as innateness, a priori knowledge, intentionality or the normativity of thought) are compatible with this naturalistic picture, or (if they are not) how they can be explained away. This programme can be seen at its clearest and most thoroughgoing in Mill, and also in the work of Hermann von Helmholtz, Herbert Spencer and William James. (See also Naturalized philosophy of science.)

Thus the emergence of these three strands of thought - metaphysical materialism, empiricism and positivism, and naturalism - can be set against the dominant idealism of the first half of the century, and each can be seen as a revival of positions from the seventeenth and eighteenth centuries, shaped by a return to views of science and its relation to philosophy that first emerged in this early modern period. Nonetheless, there are important tensions between these strands that marked nineteenth-century debate, as had been the case when these positions first emerged. One tension was between metaphysical materialism on the one hand, and positivism on the other: for, from a positivist perspective, it appeared that materialism could not be justified, as it involved claims about the ultimate nature of reality that could not be supported on the basis of normal scientific inquiry, so transcending the epistemological limits that the positivists set themselves. Likewise, positivism encouraged an instrumentalist or conventionalist conception of scientific theories that threatened to lead to a kind of anti-realist constructivism concerning the natural world, which was also at odds with materialistic realism (see Conventionalism; Duhem, P.M.M.; Le Roy, J.; Mach, E.; Poincaré, J.H.). Another tension was between positivism and empiricism, where (as Comte argued) positivism could make greater concessions to the rationalist and Kantian traditions than could an empiricist such as Mill, by accepting that scientific inquiry in fact involved observation shaped by some sort of prior theorizing. A further tension can be seen in the relation between empiricism and naturalism, for example in the way that Mill’s empiricism led to phenomenalism, which holds that minds and experiences are all that exist; but this position seems to be at odds with his commitment to naturalism, which normally involves taking the human mind to be part of the natural world realistically conceived. Finally, while Comte sought to give the scientific understanding of society and historical development its own special status, the fact that this understanding was modelled on paradigms from the natural sciences inevitably threatened to make this form of social theory reductionistic (see Positivism in the social sciences).