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mental knowledge in the principles and laws of the human frame. It is to this humbler task that I propose to confine myself in the sequel. To follow him through the details of his Method, would be inconsistent with the nature of my present undertaking.

CHAPTER FOURTH.

OF THE METHOD OF INQUIRY POINTED OUT IN THE EXPERIMENTAL OR INDUCTIVE LOGIC.

SECTION I.

Mistakes of the Ancients concerning the proper object of Philosophy.-Ideas of Bacon on the same subject.— Inductive Reasoning.—Analysis and Synthesis.—Essential difference between Legitimate and Hypothetical Theories.

I HAVE had occasion to observe more than once, in the course of the foregoing speculations, that the object of physical science is not to trace necessary connexions, but to ascertain constant conjunctions; not to investigate the nature of those efficient causes on which the phenomena of the universe ultimately depend, but to examine with accuracy what the phenomena are, and what the general laws by which they are regulated.

In order to save repetitions, I here beg leave to refer to some observations on this subject in the first volume. `I request more particularly the reader's attention to what I have said, in the second section of the first chapter, on the distinction between physical and efficient causes; and on the origin of that bias of the imagination which leads us to confound them under one common name. That, when we see two events constantly conjoined as antecedent and consequent, our natural apprehensions dispose us to associate the idea of causation or efficiency with the former, and to ascribe to it that power or energy by which the change was produced, is a fact obvious and unquestionable; and hence it is, that in all languages, the series of physical causes and effects is metaphorically likened to a chain, the links of which are supposed to be indissolubly and necessarily connected. The slightest reflection, at the same time, must satisfy us that these apprehensions are inconsistent, and even absurd; our knowledge of physical events reaching no farther than to the laws which regulate their succession; and the words power and energy expressing attributes not of matter but of mind. It is by a natural bias or association somewhat similar (as I have remarked in the section above-mentioned) that we connect our sensations of colour, with the primary quali ties of body.**

* Were it not for this bias of the imagination to identify efficient with physical causes, the attention would be continually diverted from the necessary business of life, and the useful exercise of our faculties suspended, in a fruitless astonishment at that hidden machinery, over which nature has drawn an impenetrable veil. To prevent this inconvenient distraction of thought, a farther provision is made in that gradual and imperceptible process by which the changes in the state of the Universe are, in general, ac

This idea of the object of physical science (which may be justly regarded as the ground-work of Bacon's Novum Organon) differs essentially from that which was entertained by the ancients; according to whom "Philosophy is the science of causes." If, indeed, by causes they had meant merely the constant forerunners or antecedents of events, the definition would have coincided nearly with the statement which I have given. But it is evident, that by causes they meant such antecedents as were necessarily connected with the effects, and from a knowledge of which the effects might be foreseen and demonstrated: And it was owing to this confusion between the proper objects of physics and of metaphysics, that neglecting the observation of facts exposed to the examination of their senses, they vainly attempted, by synthetical reasoning, to deduce, as necessary consequences from their supposed causes, the phenomena and laws of nature. —“Causa ea est," says Cicero, "quæ id efficit cujus est causa. Non sic causa intelligi debet, ut quod cuique antecedat, id ei causa sit; sed quod cuique efficienter antecedat. Itaque dicebat Carneades ne Apollinem quidem posse dicere futura, nisi ea, quorum causas natura ita contineret, ut ea fieri necesse esset. Causis enim efficienti

complished. If an animal or a vegetable were brought into being before our eyes, in an instant of time,—the event would not be in itself more wonderful than their slow growth to maturity from an embryo, or from a seed. But, on the former supposition, there is no man who would not perceive and acknowledge the immediate agency of an intelligent cause; whereas, according to the actual order of things, the effect steals so insensibly on the observation, that it excites little or no curiosity, excepting in those who possess a sufficient degree of reflection to contrast the present state of the objects around them, with their first origin, and with the progressive stages of their existence.

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bus quamque rem cognitis, posse denique sciri quid futu

rum esset."*

From this disposition to confound efficient with physical causes, may be traced the greater part of the theories recorded in the history of philosophy. It is this which has given rise to the attempts, both in ancient and modern times, to account for all the phenomena of moving bodies by means of impulse;† and it is this also which has sug

* De Fato, 48, 49. The language of Aristotle is equally explicit. Exisτασθαι δε οιομεθα έκαστον άπλως, αλλά μη τον σοφιστικόν τρόπον, τον κατά συμβεβηκος, όταν την τ' αιτίαν οιώμεθα γινωσκειν, δὲ ἦν το πράγμα εστιν, ότι εκείνε αιτία εστι, και μη ενδέχεται τοτ' άλλως έχειν. Sciri autem putamus unamquamque rem simpliciter, non sophistico modo, id est ex accidenti, cum putamus causam cognoscere propter quam res est, ejus rei causam esse, nec posse eam aliter se habere.--Analyt. Poster. Lib. i. cap. 2.

Nothing, however, can place in so strong a light Aristotle's idea of the connexion between physical causes and effects, as the analogy which he conceived it to bear to the connexion between the links of a mathematical chain of reasoning. Nor is this mode of speaking abandoned by his modern followers. "To deny a first cause (says Dr. Gillies) is to deny all causation: to deny axioms is, for the same reason, to deny all demonstration." (Vol. I. p. 108.) And in another passage; "We know a mathematical proposition, when we know the causes that make it true. In demonstration, the premises are the causes of the conclusion, and therefore prior to it. We cannot, therefore, demonstrate things in a circle, supporting the premises by the conclusion; because this would be to suppose, that the one proposition could be both prior and posterior to the other." (Ibid. p. 96.) (Can one mathematical theorem be said to be prior to another in any other sense, than in respect of the order in which they are first presented to our knowledge?)

See Philosophy of the Human Mind, Vol. I. Chap. i. sect. 2. With respect to the connexion between impulse and motion, I have the misfortune to differ from my very learned and highly respected friend, M. Prévost of Geneva; whose opinions on this point may be collected from the two following sentences. "La cause diffère du simple sigue précurseur,

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