1855.] On Mental Education. 481 



analogies ; to present the fundamental idea in every form, pro- 

 portion, and condition ; to clothe it with suppositions and pro- 

 babilities, that all cases may pass in review, and be touched, 

 if needful, by the Ithuriel spear of experiment. But all this 

 must be under government, and the result must not be given to 

 society until the judgment, educated by the process itself, has 

 been exercised upon it. Let us construct our hypotheses for 

 an hour, or a day, or for years ; they are of the utmost value 

 in the elimination of truth, f which is evolved more freely from 

 error than from confusion;' but, above all things, let us not 

 cease to be aware of the temptation they offer ; or, because 

 they gradually become familiar to us, accept them as established. 

 We could not reason about electricity without thinking of it as 

 a fluid, or a vibration, or some other existent state or form. 

 We should give up half our advantage in the consideration of 

 heat if we refused to consider it as a principle, or a state of 

 motion. We could scarcely touch such subjects by experiment, 

 and we should make no progress in their practical application 

 without hypothesis ; still it is absolutely necessary that we 

 should learn to doubt the conditions we assume, and acknow- 

 ledge we are uncertain, whether heat and electricity are vibra- 

 tions or substances, or either. 



When the different data required are in our possession, and 

 we have succeeded in forming a clear idea of each, the mind 

 should be instructed to balance them one against another, and 

 not suffered carelessly to hasten to a conclusion. This reserve 

 is most essential ; and it is especially needful that the reasons 

 which are adverse to our expectations or our desires should be 

 carefully attended to. We often receive truth from unpleasant 

 sources ; we often have reason to accept unpalatable truths. 

 We are never freely willing to admit information having this 

 unpleasant character, and it requires much self-control in this 

 respect, to preserve us even in a moderate degree from errors. 

 I suppose there is scarcely one investigator in original research 

 who has not felt the temptation to disregard the reasons and 

 results which are against his views. I acknowledge that I have 

 experienced it very often, and will not pretend to say that I 

 have yet learned on all occasions to avoid the error. When a 

 bar of bismuth or phosphorus is placed between the poles of a 

 powerful magnet, it is drawn into a position across the line 



