In his series of twenty lectures, Hobson attempts to define and delimit the domain of Natural Science in order to assess its the extent to which it must influence or be influenced by the spheres of religion and philosophy. In doing so he concerns himself with its historical genesis, its functions, its possibilities and its limitations.
Lectures II to IV begin with an examination of some general features of and issues relating to the Natural Sciences and the role philosophy has played in them. Lecture II characterises Natural Science as developing from a systematized continuation of the formation of the sort of common knowledge which begins with the classification of physical objects and phenomena. He then considers the degrees of abstraction and approximation found in the sciences, and the necessary limits which the conceptual schemes of Natural Science possess. He argues that while a pragmatic theory of truth in general is not acceptable, there is nevertheless a methodological pragmatism is involved in the acceptance of scientific theories as true. The following lecture attempts to show how the theories of Natural Science can be independent of ontological hypotheses, with reference to Locke, Berkeley, Poincare and Whitehead. Nevertheless, philosophical thought is indispensable, since a philosophy of nature is more than - and cannot be obtained purely from - Natural Science. In light of this, notions of causation and deterministic systems are analysed from philosophical and scientific perspectives, concluding that while representation of parts of the world through deterministic schemes is useful and appropriate for Natural Science, it remains unprovable that the world of physical phenomena can be represented as a deterministic scheme.
Hobson proceeds to deliver a series of self-contained lectures on important branches of science. He takes arithmetic to be a department of Natural Science and discusses it in Lecture V, providing an account of the notion of number and our knowledge of it. This is combined with a historical account of arithmetic, examining understandings of it amongst the Egyptians, Babylonians and Greeks, as well as later figures such as Cantor.
The following lecture examines certain philosophical conceptions of time and space, examining the concepts insofar as they appear separate to the intuitions of individuals, and their relation to Natural Science. Newton’s conception of absolute time is discussed, as is Euclidean geometry. In light of the possibility of non-Euclidean geometries, and their empirically successful use in Natural Science, Webb notes the dangers in following Kantian views of time and space as a-priori forms.
The subsequent three lectures discuss conceptions of matter, dynamics and energy. In Lecture VII Hobson suggests that although the corpuscular or atomic theories of matter appear to be fundamentally opposed to theories which hold it to be indefinitely divisible, his view of scientific theories as a conceptual representation of an assigned domain of natural phenomena allows both views to be legitimately used on different occasions for different purposes. What follows is an account of the genesis of atomic theories, from Democritus and Aristotle through to Descartes, Hobbes and Boyle, and the modifications that atomism underwent as a result of Newtonian considerations regarding forces and the acceptability of the notion of forces acting at a distance. The next lecture considers the dynamics of matter, assessing and comparing Newtonian absolutist conceptions of space and motion with relational conceptions, using the principle of inertia as illustrative. Hobson suggests that absolutist conceptions alone are inadequate. The proceeding lecture follows with an examination of the principle of conservation of matter and energy, with respect to Descartes, Newton, Boyle, Huygens and others. Understandings of the principle as one subject to empirical verification are contrasted with inadequate a priori accounts.
Lectures X-XII deal with mechanical theories and thermodynamics, electricity, magnetism and light, and the constitution of matter. The theories of Plank and Kelvin are discussed, and doubts regarding the adequacy of theories which only contemplate continuous transformations of energy are raised in light of Poincare’s appraisal of Planck’s theory. The development and eventual convergence of theories of electricity, magnetism and light into the electromagnetic theory of light is charted, and Webb suggests that as far as Natural Science is concerned, the metaphysical assessment of the relation of these theories to “reality” is of no direct bearing. Lecture XII then describes the evolution of modern atomic theories, and charts the convergence of physics and chemistry in the development of the theories of radioactivity, electrons and nuclei.
Lectures XII and XIV move from the microcosmic level to the macrocosmic branches of science, namely cosmical theories of the processes of the solar system and stellar universe, and Einstein’s theory of relativity. He begins with a description of the solar system, and surveys the speculations and hypotheses of Kant and Laplace before detailing the progress of this branch of Natural Science. Hobson notes the speculative character of such branches of Natural Science, in contrast to the sorts of theories that are capable of more direct verification as examined in previous lectures. He then discusses the epistemological status of Einstein’s theory of relativity in light of its abstract mathematical nature, and its apparently novel relation to philosophy.
Lecture XV discusses Biology as a general branch of science, detailing its methods and limitations. He argues that just as we must in ordinary life, Biology must adhere a methodological dualism in which the domains of the physical and mental are provisionally separated. The following lecture examines the key notion in biology, namely that of the living organism. He charts the historical path of scientific understandings of the living organism, starting with Aristotle and finishing with contemporary cell-theory and its limitations. After a lecture on heredity and the rejection of traditional views regarding the spontaneous generation of life, Hobson discusses Darwin’s theory of the evolution of the species and the origin of the theory in Aristotle, St. Augustine and Lamarck. The effect of the anti-teleological tendency of Darwin’s theory is highlighted, and the division between the Neo-Darwinian and Neo-Lamarckian views of evolution regarding natural selection and acquired characteristics is used to explain the development of evolutionary theories.
A survey of the relevant branches of Natural Science complete, in the final two lectures Hobson outlines his conception of the relation of Natural Science to general thought, and then to theism. He explains his view of Natural Science as circumscribed and restricted by its method, its sphere of application and the type of knowledge with which it is concerned. Only with philosophy, religion and art do values become significant, and their domains are not the same as that of Natural Science. Science and religion require philosophy in order for them to be related. Religion and philosophy involve views of reality, and these must not be incompatible with an autonomous Natural Science. It is philosophy that informs this relation. The philosopher and theologian are concerned with “the secret of the Universe”, though it has not been revealed to him. Though there can be interactions between religion and science, in the domain of Natural Science, the scientist is not concerned with any such 'secrets'.