naturam se applicare possit. This Logic boasts itself to be a key to every science, since it directs and strengthens the thinking mind in its striving after knowledge: Rationales scientiae reliquarum omnino claves sunt; atque quemadmodum manus instrumentum instrumentorum, anima forma formarum, ita et illae artes artium ponendae sunt. Neque solum dirigunt, sed et roborant, sicut sagittandi usus non tantum facit, ut melius quis collineet, sed ut arcum tendat fortiorem. In the Nov. Org. Bacon asserts that his inductive method is applicable to the intellectual and moral sciences, but does not proceed to apply it. This application was only 'a dark presentiment from afar '(Beneke). Bacon has seldom given the correct methods of investigation in particular cases, still seldomer reached good scientific results in his investigations, and has not even recognised as valuable nor appropriated the best of the discoveries already made in his day by others (all which Lasson and Liebig have made manifest, while they were opposing the previously very widely-extended overestimation of Bacon); but he did this service, he more strongly opposed than any of his predecessors the trivialities of Scholasticism, he firmly established universal laws of inductive investigation, and he gave a place in Logic to the new tendency, with its methods and principles. Cf. § 134, on Hypothesis and the Experimentum crucis.' § 24. If Bacon paid almost exclusive attention to sense-perception and outer nature, Des Cartes (15961650), on the other hand, found in the inherent certainty of the thought of his own existence the one startingpoint of philosophical knowledge which could withstand every doubt. He made the subjective clearness and distinctness the criterion of objective truth, and found security for the validity of this criterion in the divine truthfulness, which could not allow a clear and 2 Ibid. i. 127. 1 De Augm. v. 1. Des Cartes distinct conception to be a deceptive one. accordingly believes that by means of this criterion the human mind can truly know both its own thinking in the widest sense of the word, or its whole inner conscious activity, the divine nature, and, as the properties of extended things, extension in space and its modes. He calls immediate knowledge Intuition; every mediate way of knowledge he comprehends under the general notion of Deduction. In mediate knowledge Des Cartes occasionally distinguishes a double method of exhibiting his fundamental doctrines-the analytic and the synthetic: the former, which proceeds from what is immediately given to principles, serves for discovery; the latter, which proceeding from principles deduces single theorems, serves for strict demonstration. Des Cartes believes that in four general directions he exhausts all that can be said about method. The first rule demands evidence which is founded on perfect clearness; the second, a division of the difficulties; the third, an orderly; and the fourth, a continuous advance in investigation. Every error is due to an abuse of the freedom of the will, leading to hasty judgment. Des Cartes enunciates the following definition of Clearness and Distinctness :-Claram voco illam perceptionem, quae menti attendenti praesens et aperta est, distinctam autem illam, quae quum clara sit, ab omnibus aliis ita seiuncta est et praecisa, ut nihil plane aliud, quam quod clarum est, in se contineat. The four rules of method (which are not so much logical laws as rules, which we must receive subjectively in order to be able to comply with the logical standard, and so escape errors) are to be found in Princip. Phil. i. § 45. Discours de la Méthode pour bien conduire sa la vérité dans les Sciences, 1637,' sec. part. raison et chercher Thus, instead of the great number of precepts of which Logic is made up, I thought that the four following would be sufficient, provided I firmly and constantly resolved not to fail even once in observing them. The first was, never to accept anything as true, unless I recognised it to be so evidently, i.e. to avoid carefully haste and anticipation, and to include nothing in my judgments but what should present itself so clearly and distinctly to my mind that I should have no occasion to doubt it. The second was, to divide each of the difficulties I had to examine into as many parts as would be requisite for better resolving them. The third was to arrange my thoughts in an orderly fashion, beginning with the most simple objects, and those most easily understood, to ascend little by little, by degrees as it were, up to the knowledge of the most compound, and to imagine an order even between those which do not precede each other naturally. And the last was, to make everywhere such complete enunciations and such general reviews, that I should be certain I had omitted nothing.' In the same place, Des Cartes says of the Syllogism, and of most of the other doctrines of Logic, that they have more a didactic than a scientific value: As for Logic, its syllogisms and the majority of its other precepts are of avail rather in the communication of what we already know than in the investigation of the unknown.' Des Cartes touches upon the distinction between Analytic and Synthetic methods in his replies to objections against his Meditationes de Prima Philosophia, Respons. ad secund. obiect. In the treatise, Regulae ad Directionem Ingenii (first published in his Opuscula Posthuma, Amstelod. 1701), Des Cartes distinguishes Intuition, or Knowledge immediately certain, by which we become conscious of principles, and Deduction, or the operation by which we deduce a knowledge, which is the necessary consequent of an other, and recognise it because of the other. The demands contained in the 1 Discursus de Methodo recte utendi Ratione, 1644. [Translated into English by Prof. Veitch, p. 61, Edin. 1863.] four directions for method in the Discours are further developed by Des Cartes into rules when he applies them to single philosophical, and especially mathematical, problems. The most celebrated logical work which has proceeded from the School of Des Cartes is La Logique, ou l'art de penser, Paris, 1662,' in which the doctrines of Aristotle are combined with the principles of Des Cartes. It defines Logic to be the art of the right use of reason in the knowledge of things (l'art de bien conduire sa raison dans la connaissance des choses, tant pour s'instruire soi-même que pour en instruire les autres). This work is probably due to Antony Arnauld, assisted by Nicole and other Jansenists of the Port-Royal. Nicole Malebranche (1638-1715), the representative of the doctrine that we see all things in God, in his work, De la Recherche de la Vérité, Paris, 1673, proceeds upon the fundamental principles of Des Cartes. Among the opponents of Des Cartes, Gassendi (1592–1655) deserves special mention for his clear and well-arranged representation of Logic. § 25. Spinoza (1632-1677) traced false or inadequate knowledge to the influence of the imagination, true or adequate knowledge to thought. Truth is the agreement of the idea with its object. Truth makes clear both itself and error. The intuitive understanding recognises each individual from its causes, and the finite generally from the infinite. It attends, in the first place, to the idea of one substance whose essence includes in it existence, in order to know thought and existence as its attributes, and individual beings as their modes. The arrangement and connection of thoughts correspond to the arrangement and connection of things. The philosophical method is identical with the mathematical. [Translated into English by Prof. Baynes, 2nd ed. 1851, Edin.] Of the works of Spinoza, the Tractatus de Intellectus Emendatione, in the Opera Posthuma, Amstelod. 1677, belongs Several passages in the Ethics The fundamental postulate of omnino referat naturae exem more especially to our subject. are to be compared with it. Spinoza is: Ut mens nostra plar, debet omnes suas ideas producere ab ea, quae refert originem et fontem totius naturae, ut ipsa etiam sit fons ceterarum idearum.' He defines truth to be convenientiam ideae cum suo ideato.' He distinguishes three kinds or grades of knowledge imaginatio (pavraoia), ratio (the ιστýμn of Aristotle), and intellectus (the intuitive knowledge of principles, almost equivalent to the Aristotelian voûs). The philosopher considers all things as moments of one substance, sub specie aeternitatis. The concatenatio intellectus' should 'concatenationem naturae referre.' Kuffeler treats of the method of philosophical investigation from the stand-point of Spinoza, in his Specimen Artis Ratiocinandi naturalis et artificialis, ad pantosophiae principia manducens, Hamb., 1684. § 26. Locke (1632-1704), applying the method of Bacon to the objects of inner experience, investigated the psychological problem of the origin of human knowledge, with the view of reaching a sure fundamental position for the decision of the logical question (of the question belonging to the theory of knowledge) of the objective truth of our notions. Locke distinguished sensation or sense-perception from reflection or perception of the inner activities to which the soul is aroused on occasion of the outer affections. From these two sources all conceptions arise. There are no 'innate ideas.' Nihil est intellectu, quod non fuerit in sensu. Locke, like Des Cartes, attributes full truth to the internal perceptions, partial truth only to the external. Locke, by his results, was the forerunner of the sensationalism of |