along with this indistinctness of ideas which we are endeavouring to explain.

4. Indistinctness of Ideas in Astronomy.-Returning to the sciences, it may be supposed, at first sight, that, with regard to astronomy, we have not the same ground for charging the stationary period with indistinctness of ideas on that subject, since they were able to acquire and verify, and, in some measure, to apply, the doctrines previously established. And, undoubtedly, it must be confessed that men's notions of the relations of space and number are never very indistinct. It appears to be impossible for these chains of elementary perception ever to be much entangled. The later Greeks, the Arabians, and the earliest modern astronomers, must have conceived the hypotheses of the Ptolemaic system in a tolerably complete degree. And yet, we may assert, that, during the stationary period, men did not possess the notions, even of space and number, in that vivid and vigorous manner which enables them to discover new truths. If they had perceived distinctly that the astronomical theorist had merely to do with relative motions, they must have been led to see the possibility, at least, of the Copernican system; as the Greeks, at an earlier period, had already perceived it. We find no trace of this. Indeed the mode in which the Arabian mathematicians present the solutions of their problems, does not indicate that clear apprehension of the relations of space, and that delight in the contemplation of

them, which the Greek geometrical speculations imply. The Arabs are in the habit of giving conclusions without demonstrations, precepts without the investigations by which they are obtained; as if their main object were practical rather than speculative, the calculation of results rather than the exposition of theory. Delambre has been obliged to exercise great ingenuity, in order to discover the method in which Ibn Iounis proved his solution of certain difficult problems.

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5. Indistinctness of Ideas shown by Sceptics.-The same unsteadiness of ideas which prevents men from obtaining clear views, and steady and just convictions, on special subjects, may lead them to despair of or deny the possibility of acquiring certainty at all, and may thus make them sceptics with regard to all knowledge. Such sceptics are themselves men of indistinct views, for they could not otherwise avoid assenting to the demonstrated truths of science; and, so far as they may be taken as specimens of their contemporaries, they prove that indistinct ideas prevail in the age in which they appear. In the stationary period, moreover, the indefinite speculations and unprofitable subtleties of the schools might further impel a man of bold and acute mind to this universal scepticism, because they offered nothing which could fix or satisfy him. And thus the sceptical spirit may deserve our notice as indica

Delamb. M. A. p. 125-8.

tions of the defects of that system of doctrine which was too feeble in demonstration to control such resistance.

The most remarkable of these philosophical sceptics is Sextus Empiricus; so called, from his belonging to that medical sect which was termed the empirical, in contradistinction to the rational and methodical sects. His works contain a series of treatises, directed against all the divisions of the science of his time. He has chapters against the Geometers, against the Arithmeticians, against the Astrologers, against the Musicians, as well as against Grammarians, Rhetoricians and Logicians; and, in short, as a modern writer has said, his scepticism is employed as a sort of frame-work which embraces an encyclopedical view of human knowledge. It must be stated, however, that his objections are rather to the metaphysics, than to the details of the sciences; he rather denies the possibility of speculative truth in general, than the experimental truths which had been then obtained. Thus his objections to geometry and arithmetic are founded on abstract cavils concerning the nature of points, letters, unities, &c. And when he comes to speak against astrology, he says, "I am not going to consider that perfect science which rests upon geometry and arithmetic ; for I have already shown the weakness of those sciences; nor that faculty of prediction (of the motions of the heavens) which belongs to the pupils of Eudoxus, and Hipparchus, and the

rest, which some call astronomy; for that is an observation of phenomena, like agriculture or navigation; but against the art of prediction from the time of birth, which the Chaldeans exercise." Sextus, therefore, though a sceptic by profession, was not insensible to the difference between experimental knowledge and mystical dogmas, though the former had nothing which excited his admiration.

The early writers of the Christian church deemed lightly of the philosophy of their pagan antagonists; but this was on different grounds, as we shall hereafter see. The spirit of bold examination and denial of authority appears to be still more uncongenial to the Mohammedan temper of thought; yet one remarkable sceptic with regard to philosophy can be pointed out among the Saracen writers. This is Algazel, or Algezeli, who was a celebrated teacher at Bagdad in the eleventh century, and who declared himself the enemy, not only of the mixed peripatetic and Platonic philosophy of his time, but of Aristotle himself. His work, entitled "The Destructions of the Philosophers," is known to us by the refutation of it which Avicenna published, under the title of "Destruction of Algazel's Destructions of the Philosophers." It appears that he contested the fundamental principles of the Platonic and Aristotelian schools, and denied the possibility of a known connexion between cause and effect; thus making a prelude to the celebrated argumentation of Hume.

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* Degerando, Hist. Comp. des Syst. iv. 124.

In his work "On the Opinions of the Philosophers," he examined those opinions in particular which refer to the principles of the physical sciences. We cannot doubt that his objections, so far as they attacked the really-established truths of astronomy and other sciences, must have implied confusion of apprehension both in him and in those whom he persuaded.

6. Neglect of Physical Reasoning in Christendom. If the Arabians, who, during the ages of which we are speaking, were the most eminent cultivators of science, entertained only such comparatively feeble and servile notions of its doctrines, it will easily be supposed, that in the Christendom of that period, where physical knowledge was comparatively neglected, there was still less distinctness and vividness in the prevalent ideas on such subjects. Indeed, during a considerable period of the history of the Christian church, and by many of its principal authorities, the study of natural philosophy was not only disregarded but discommended. The great practical doctrines which were presented to men's minds, and the serious tasks, of the regulation of the will and affections, which religion impressed upon them, made inquiries of mere curiosity seem to be a reprehensible misapplication of human powers; and many of the fathers of the church revived, in a still more peremptory form, the opinion of Socrates, that the only valuable philosophy is that which teaches us our moral duties and religious hopes. Thus Euse

5 Brucker iii. 317.