428 NEW BOOKS. Prof. Guastella is a positivist of the positivists, one who pushes positivism to its furthest logical consequences. Not merely does he resolve our knowledge of causation into the recognition of invariable phenomenal successions, but he maintains that no other causes can be known, for the good reason that no other causes exist or can be con- ceived. But, granting so much, the question presents itself, how to account for the claim of metaphysics to go behind appearances and to present a satisfying explanation of the realities which are supposed to underlie them. According to our author the answer is to be found in a tendency which leads the human mind to interpret what is unfamiliar by the analogy of what is familiar, combined with the idea that familiarity is itself an explanation, that when one event has always succeeded another in our daily experience we accept this constancy as a sufficient reason for its occurrence. It is to this law of mind that the notion of efficient causation owes its origin. An efficient cause is a cause explain- ing its effect, a something from our knowledge of which the effect could be deduced a priori and independently of experience. Agnostics from Locke to Spencer, while denying that we can have such knowledge still allow the actual or possible existence of agencies that would put us in possession of it were they within the range of our observation and reasoning. But the philosopher who has learned to interpret the notion of cause in terms of simple sequence ought to understand that behind sequences there is nothing the discovery of which would explain them. The supposed hidden causes, were they disclosed, would be merely so many additional facts of experience. The earliest and most familiar of all experiences is the power of voluntary motion ; and for no other reason than its familiarity this power is accepted as self-evident. Thus for primitive man will becomes the type on which all explanations of unfamiliar happenings are modelled. Hence arise the various anthropomorphic theories of nature, from savage animism up to the most elaborate metaphysical theologies, and not theo- logies only but also the atheistic hylozoisms which, like Clifford's theory of mind-stuff, assume that the universe would be more intelligible if it consisted of nothing but conscious elements. Another experience, only less familiar than voluntary action, is that the bodies without us move under the stress of their mutual impacts and pressures ; and that this should be so is also assumed as self-evident from its habitual occurrence. Accordingly all the thorough-going systems of materialism explain natural events as more or less complicated atomic shocks, without considering that for bodies to move each other after contact is in itself no more intelligible than that they should move one another at a distance. So strong indeed is the primary instinct of assimilation that it over- rides and reverses man's original animistic philosophy. The spirit or consciousness to whose initiative all motion was once ascribed is in course of time declared incapable of acting on matter at all, or of being acted on by it. Hence arise theories of automatism and parallelism which Prof. Guastella regards as based on a fundamental fallacy the fallacy that an effect must be explicable by its cause. And he makes this same fallacy responsible for the various metaphysical systems in which nature is constructed a priori, or in which such a construction is set up as the supreme ideal of knowledge. Of these the most typical instances are to be found in what he calls dialectic realism, a method to whose exposure his whole second volume is devoted. As is well known, Auguste Conite identifies metaphysics with the ex- planation of phenomena by realised abstractions ; and he regards this method as a necessary stage in the evolution of thought. But this the
