KNOWLEDGE AND FAITH. 513 
that seems doubtful to another, while other truths may be clearly perceived by the second 
that are very obscure to the first. For this difference of perception there seems to be no 
remedy, and hence it is impossible to frame any system of mental science that shall com- 
mend itself equally to all. 
208. But if each individual would study carefully the workings of his own mind, he 
would probably find that the same extent of truth is attainable in metaphysics as in 
mathematics, and that all the great problems of our spiritual nature, and of spiritual ex- 
istence in general, are as indubitable as the simplest propositions of geometry, provided 
we pursue our investigations with the requisite diligence.* 
209. To one man it may be self-evident that there can be no effect without a cause, 
and it may also be self-evident that intelligence is the highest possible cause. If he com- 
pares these two axioms, he will demonstrate to himself, from their self-evident relation, 
the existence of an intelligent God, and the demonstration will be entirely and mathe- 
matically rigorous. 
210. To another man the existence of an intelligent Deity may be demonstrable by the 
comparison of other truths, which are his axioms, while to a third, the Divine existence 
may itself be axiomatic. But it can hardly be expected that the train of reasoning adopted 
by either of the three, will be satisfactory or conclusive to the others, for that is self-evi- 
dent to one, and therefore incapable of proof, for which the mental constitution of another 
requires demonstration. 
211. The investigation of spiritual truth is therefore full of intricacy. The best spiritual 
_ guides are but imperfectly acquainted with the way in which they would lead us, and we 
must consequently learn to place dependence on ourselves, or rather on the revelations 
that may be made to us. Self-evidence, as we have seen, is the only test of knowledge, 
and whenever any truth, simple or complex, becomes self-evident, or is the self-evident 
result of various self-evident relations, we shall feel that no one can deny it. If any 
profess to disbelieve it, we shall know that they do not comprehend it, and if any chance 
to assert that they know it is false, we shall know that they do not understand our 
meaning. 
* Cousin gives the following as instances of metaphysical axioms. “Quality supposes a subject, succession 
supposes time, body supposes space, the finite supposes the infinite, variety supposes unity, phenomenon supposes 
substance and being.” Hist. of Mod. Phil., Vol. II, p. 283. 
