Bacon emphasizes what has reference to the formal aspect of investigation. For he says, “Natural philosophy is divided into two parts, the first consists in the investigation of causes; the second in the production of effects; the causes to be investigated are either final or formal causes, or else material or efficient causes. The former constitutes metaphysics; the latter physics. This last Bacon looks upon as a branch of philosophy very inferior in point of dignity and importance to the other and accordingly to ascertain the most probable means of improving our knowledge of metaphysics is the great object of his _Organon_.”[107] He himself says: “It is a correct position that ‘true knowledge is knowledge by causes. And causes, again, are not improperly distributed into four kinds: the material, the formal, the efficient, and the final.’”[108] (Vol. I. p. 174, Vol. II. p. 138.) But in this connection an important point is that Bacon has turned against the teleological investigation of nature, against the investigation into final causes. “The investigation of final causes is useless; they corrupt rather than advance the sciences except such as have to do with human action.”[109] To Bacon the important matter is to investigate by the study of _causæ efficientes_. To the consideration of final causes such assertions as these belong: “That the hairs of the eyelids are for a protection to the eyes; that the thick skins and hides of living creatures are to defend them from heat and cold; that the trees have leaves so that the fruit may not suffer from sun and wind”[110]: the hair is on the head on account of warmth; thunder and lightning are the punishment of God, or else they make fruitful the earth; marmots sleep during the winter because they can find nothing to eat; snails have a shell in order that they may be secure against attacks; the bee is provided with a sting. According to Bacon this has been worked out in innumerable different ways. The negative and external side of utility is turned round, and the lack of this adaptation to end is likewise drawn within the same embrace. It may, for example, be said that if sun or moon were to shine at all times, the police might save much money, and this would provide men with food and drink for whole months together. It was right that Bacon should set himself to oppose this investigation into final causes, because it relates to external expediency, just as Kant was right in distinguishing the inward teleology from the outward. As against the external end, there is, in fact, the inward end, _i.e._ the inward Notion of the thing itself, as we found it earlier in Aristotle (Vol. II. pp. 156-163). Because the organism possesses an inward adaptation to its ends, its members are indeed likewise externally adapted as regards one another; but the ends, as external ends, are heterogeneous to the individual, are unconnected with the object which is investigated.