430 Dr. St. George Mivart [June 5, 



to give a vigorous assent to anything. It is necessary distinctly 

 to recognise there is such a thing as legitimate certainty, not to 

 perceive the force of which is illegitimate doubt. Such doubt would 

 necessarily discredit all physical science. Universal doubt, for 

 example, is an absurdity — it is scepticism run mad. If any one 

 affirms that "nothing is certain," he obviously contradicts himself, 

 since he thereby affirms the certainty of uncertainty. He says that 

 which if true absolutely contradicts what he has declared to be true. 

 But a man who affirms what the system he professes to adopt 

 forbids him to affirm, and who declares that he believes what he also 

 declares to be unbelievable, should hardly complain if he is called 

 foolish. No system can be true, and no reasoning can be valid, 

 w^hich inevitably ends in absurdity. Such scepticism, then, cannot 

 be the mark of an exceptionally intellectural mind, but of an excep- 

 tionally foolish one, and every position which necessarily leads to 

 scepticism of this sort must be an untenable position. 



A very little reflection suffices to show how self-refuting such 

 modes of thought are : Thus, if a man were to say — " I cannot know 

 anything, because I cannot be sure that my faculties are not always 

 fallacious," or " I cannot be sure of anything because, for all I know, 

 I may be the plaything of a demon who amuses himself by constantly 

 deceiving me " — in both these cases he contradicts himself. He con- 

 tradicts himself because he obviously grounds his assertion upon his 

 perception of the truth that " we cannot arrive at conclusions which 

 are certain, by means of principles which are uncertain or false." But 

 if he knows that truth he must know that his faculties are not always 

 fallacious and that his demon cannot deceive him in everything. 



My object in making these remarks is to enable us to get clear of 

 mere idle, irrational doubts which have no place in science, and can 

 have none, so that we may recognise the fact that we all of us have 

 certainty as to some facts according to our degrees of knowledge. 

 Obviously we can only judge of truth by our mental faculties, and if 

 a man denies their validity we must pass him by, contenting ourselves 

 with calling his attention to the fact that he refutes himself. If a 

 man professes to doubt his faculties, or to doubt whether language 

 can be trusted to convey thought, then plainly we cannot profitably 

 argue with him. But if, on account of his absurdity, we cannot 

 refute him, it is no less plain that he cannot defend his scepticism. 

 Were he to attempt to do so, then he would show, by that very 

 attempt, that he really had confidence in reason and in language, 

 however he might verbally deny it. Confident, then, that there are 

 some scientific statements on which we may rely with certainty, let us 

 consider a few truths implicitly contained in them. 



In the first place, science makes use not only of observations and 

 experiments, but also of reasoning as to the results of such experiments. 

 It needs that we should draw valid inferences ; but this implies that 

 we may, and must, place confidence in the principle of deduction — in 

 that perception of the mind which we express by the word " therefore." 



