But the reason which leads many to persuade them selves that there is a difficulty in knowing this truth,and even also in knowing what their mind really is,is that they never raise their thoughts above sensible objects,and are so accustomed to consider nothing except by way of imagination,which is a mode of thinking limited to material objects,that all that is not imaginable seems to them not intelligible.The truth of this is sufficiently manifest from the single circumstance,that the philosophers of the schools accept as a maxim that there is nothing in the understanding which was not previously in the senses,in which however it is certain that the ideas of God and of the soul have never been;and it appears to me that they who make use of their imagination to comprehend these ideas do exactly the some thing as if,in order to hear sounds or smell odors,they strove to avail themselves of their eyes;unless indeed that there is this difference,that the sense of sight does not afford us an inferior assurance to those of smell or hearing;in place of which,neither our imagination nor our senses can give us assurance of anything unless our understanding intervene.
Finally,if there be still persons who are not sufficiently persuaded of the existence of God and of the soul,by the reasons I have adduced,I am desirous that they should know that all the other propositions,of the truth of which they deem themselves perhaps more assured,as that we have a body,and that there exist stars and an earth,and such like,are less certain;for,although we have a moral assurance of these things,which is so strong that there is an appearance of extravagance in doubting of their existence,yet at the same time no one,unless his intellect is impaired,can deny,when the question relates to a metaphysical certitude,that there is sufficient reason to exclude entire assurance,in the observation that when asleep we can in the same way imagine ourselves possessed of another body and that we see other stars and another earth,when there is nothing of the kind.For how do we know that the thoughts which occur in dreaming are false rather than those other which we experience when awake,since the former are often not less vivid and distinct than the latter?
And though men of the highest genius study this question as long as they please,I do not believe that they will be able to give any reason which can be sufficient to remove this doubt,unless they presuppose the existence of God.For,in the first place even the principle which I have already taken as a rule,viz.,that all the things which we clearly and distinctly conceive are true,is certain only because God is or exists and because he is a Perfect Being,and because all that we possess is derived from him:whence it follows that our ideas or notions,which to the extent of their clearness and distinctness are real,and proceed from God,must to that extent be true.Accordingly,whereas we not infrequently have ideas or notions in which some falsity is contained,this can only be the case with such as are to some extent confused and obscure,and in this proceed from nothing (participate of negation),that is,exist in us thus confused because we are not wholly perfect.And it is evident that it is not less repugnant that falsity or imperfection,in so far as it is imperfection,should proceed from God,than that truth or perfection should proceed from nothing.But if we did not know that all which we possess of real and true proceeds from a Perfect and Infinite Being,however clear and distinct our ideas might be,we should have no ground on that account for the assurance that they possessed the perfection of being true.
But after the knowledge of God and of the soul has rendered us certain of this rule,we can easily understand that the truth of the thoughts we experience when awake,ought not in the slightest degree to be called in question on account of the illusions of our dreams.For if it happened that an individual,even when asleep,had some very distinct idea,as,for example,if a geometer should discover some new demonstration,the circumstance of his being asleep would not militate against its truth;and as for the most ordinary error of our dreams,which consists in their representing to us various objects in the same way as our external senses,this is not prejudicial,since it leads us very properly to suspect the truth of the ideas of sense;for we are not infrequently deceived in the same manner when awake;as when persons in the jaundice see all objects yellow,or when the stars or bodies at a great distance appear to us much smaller than they are.For,in fine,whether awake or asleep,we ought never to allow ourselves to be persuaded of the truth of anything unless on the evidence of our reason.And it must be noted that I say of our reason,and not of our imagination or of our senses:thus,for example,although we very clearly see the sun,we ought not therefore to determine that it is only of the size which our sense of sight presents;and we may very distinctly imagine the head of a lion joined to the body of a goat,without being therefore shut up to the conclusion that a chimaera exists;for it is not a dictate of reason that what we thus see or imagine is in reality existent;but it plainly tells us that all our ideas or notions contain in them some truth;for otherwise it could not be that God,who is wholly perfect and veracious,should have placed them in us.And because our reasonings are never so clear or so complete during sleep as when we are awake,although sometimes the acts of our imagination are then as lively and distinct,if not more so than in our waking moments,reason further dictates that,since all our thoughts cannot be true because of our partial imperfection,those possessing truth must infallibly be found in the experience of our waking moments rather than in that of our dreams.
