A compendium of Logick, According to the modern Philosophy, extracted from Le-grand; & others their Systems.
The Prolegomenon
Chap. 1. of the nature and constitution of Logic
Man’s mind being obnoxious to much error both in its searches for truth, and pursuits after that which is good, two arts have been sought out; the one to aid the understanding, the other to direct the will; this being called Ethicks; that Logick.
Def: Logic is an Art of thinking; or, to the same effect, An Art of using our Reason for the obtaining of knowledge; for we are not to limit this term [thinking] to an Apprehending of simple Idea’s, but so to extend it as therein to Include Judgment & discourse, and this we may {doe} without Prejudice to Accurracy, Since it is a truth that to discourse, to Judge and to conceive are only different modes of thinking: some Add [rectè] & Define Logick, An Art of thinking well; which altho it makes a better sound, and at first sight may seem needful, yet on due Search is found to be needless, yea Inaccurate; the reason is because [As Aristotle observed] the mode or method is Implyed Sufficiently in the word [Art] And hence [whether we mind it or no] it is usuall with us to say [An Art of painting; An Art of numbering. &.] not expressing the Adverb; and yet we think it Impossible that any Should misunderstand us and conceive of A painting ill, or numbering wrong when we thus barely deliver our Selves. Objt: The object of Logick is every thing knowable; or every thing that may be proposed to the understanding of man; not as if, Logick did Instruct the mind about the nature of things, or of any one thing: [this is the Design of Philosophy] but in that it makes the way clear for knowledge in generall, and delivers such precepts as may direct (&) assist the mind, when enquiring Into the nature of any thing Whatever.
In order to mans using his Right Reason, its necessary that he perceives, that he Judges, that he discourses, & that he Methodises.
Percpt: Perception (or Apprehension) is the Simple contemplation of things which are in the mind: thus we consider, the Earth, the Sun, A tree, Rotundity &c. not pronouncing any thing concerning them whether good or bad.
¶ that the form, under which we consider those things is called an Idea. Judgmt. Judgment is that operation of the mind by which coupling divers Idea’s we affirm or deny that this is that: thus, considering the Idea of the Earth & the Idea of Roundness we affirm or deny that the earth is round. Disc: Discourse is that operation of the mind, by which out of many Judgments we draw another; thus, when we have Judged that man has Reason, & that Socrates is a man, we may Infer that Socrates has Reason. Meth: Method [or Disposition] is that operation of the mind, by which we dispose, the various Idea’s, Judgments & Reasonings which we have of one and the same Subject, in Such order as is most suitable for the explaining of it.
Hence [According to the 4 operations of mans mind] Logick ought to be divided Into four parts; the first, Respecting Idea’s, or the simple Apprehensions of things: the second, Respecting Judgments or Propositions in which there is truth or falshood: the third, Respecting discourse or syllogisms: the fourth and last part, Respecting method, or an orderly disposing of our thoughts, by which [as by so many steps] we obtain the way of knowledge: by the first we are put upon Attention and consideration; by the second we are freed from doubts and errors, by the third, we are accustom’d to Reason; by the fourth, we Infallibly prove a truth, and demonstrate the same to others
Cap. 2. Of the use & benefit of Logick.
Logick is no less helpfull to the mind than Physick is to the body of man; & in that the mind is more noble Than the body & its diseases more latent and with greater Difficulty discovered than those of the body are: It seems but Reasonable, that Logick should have the pre-eminence; notwithstanding, our Experience teaches [what ever the Reason is] that the Physitian bares the name, and that this other Artist is of Low Repute in the world. Some (perhaps) will pretend the Reason to be, In that Althô Physick is Immediately designed only for the Body, yet the virtues thereof do greatly Influence the mind of man, It being not so with this Art; since althô it may benefitt the mind, and that in no Small degree, yet as to the body is altogether useless and uninstructive, and Indeed, were the Hypotheses undoubtedly true [which now we cannot enquire after] and the reason proposed not only pretended, but also the true and adequate Reason, it would prove the best salve Imaginable, and [for ought we know] Sufficiently Justifies the practice reflected on: Whereas should it appear, that the undervaluing this noble Art has its Root in Sensuality, and is grounded on an expectation of meeting with bliss and content in an Animal life, or [which is all one] the health & prosperity of the body, we could not but condemn this practice and censure it as highly absurd and unreasonable.
Lest we should Run Into a mistake here, It is to be noted that when we Assert Logick to be medicinal to the mind of man, we mean not, with Respect to Sin & moral defects, [for the curing of Which Theology & Ethicks take Sufficient care] but with Respect to those defects that attend the mind in perceiving of things; Such as, Ignorance & oblivion, doubting and error, confusion & obscurity and the like.
It may (perhaps) be objected, that nature [or more naturall Logick] being our guide, the forementioned operations of the mind may be performed, and consequently that it is absurd to talk of an Art for this end; And it cannot deny [Since experiences abundantly prove it] but that some who are unaquainted with the precepts of this Art may know more, and pass a better Judgment on things, than some who are acquainted therewith; but notwithstanding our concession, We answer, that the objection is weak & insignificant; and The Invalidity thereof appears even from this consideration: viz: that no man can use his reason so well naturally, but that by acquaintance with this Art he might use it much better: so that althô Reason innate with us is the foundation here [and is it not so with respect to all Arts?] yet the Art of Reason may be fairly fram’d and superstructed: And this Art is profitable unto us particularly in 3 Respects:
- 1. In that hereby we may come to a certain knowledge that we use our Reason, for he that follows these rules leaves no room for doubt.
- 2. In that hereby we may the more easily detect & explain the Defects that may be Incident to our minds: It is no unusuall thing for a man to be able to Judge that there is a fallacy in this or that argumentation, whence it will exceed the power of his nature to detect & confute the supposed fallacy; Just like the unskillfull person who viewing a draught of the Limner shall presently tax it with Imperfection and say that this is not right, that that is not accurate; and yet shall be altogether uncapable either of mending what is amiss, or of describing to another wherein the fault dos lie; Whereas the Artist [whose Reason is advanced] will readily discover all Error, and by help of his rules as readily correct and amend the same.
- 3. In that hereby we are brought to a more thorough acquaintance with our own minds: when we have considered the divers operations of the mind and acquainted our selves with it’s diseases, and with it’s cures, It becomes Impossible that we should be ignorant of the more noble part with us.
Cap. 3. of Some generall observables, or, Rules of truth.1
It is the part of a skilfull Physitian when about to eradicate any distemper or remove any illness, first to prepare the body & to leave some generall directions which may be of use to his design; in Imitation of which practice, we shall here propose some Generall rules or observables which may be no less helpfull to us in our present design of bringing the soul to it’s healthfull estate.
First Rule of Truth
Nothing is to be admitted for truth which Includes any thing of doubt in it.
We are taught even by the light of nature that all doubting prevents knowledge, and that we cannot Possibly attain thereto till the thing Apprehended is without obscurity or confusion perceived by the mind, and therefore it can be no rashness to reject all doubt as adulterated images, that would lead us into error.
Corol: hence (if we would Phylosophize in earnest) we must lay aside all the prejudices of Infancy and youth, for in that they crept into our minds Antecedancously to a due search and examination by Reason, (at least as to us) it is possible that they may be false and consequently there is sufficient Reason for our doubting about and rejecting of them.
This method in obtaining knowledge is not peculiar to Descartes but was approved of by Aristotle, as may be seen in his 3 book of Metaphysicks. chapter 1.2
¶ that he that doubts of things only to please an humour, or to the end that he may be said to doubt of them, may properly be termed a Sceptick and censured for folly & unreasonableness. Whereas to doubt of things and to suppose them to be all false only for the obtaining a more full and distinct knowledge is a laudable method very much preventive of error and false Judgments: and this our method seems to us to be of the like nature with that most harmless practice of the Astronomer who Imagines and Supposes an Equator a Zodiack and other Circles to be in the heavens to the end that he may the more accurately describe the course and motion of the Sun and the other Celestiall bodies.
The Second Rule of truth
Let us be Cautious how we give credit unto the Senses. Our senses both external and Internal are all Deceitfull and oftentimes lead us into error; thus: to the eye a square tower, being high appears round, and thô Sun as tho not above a foot or two diameter;—to the ear, some thunder sounds like a canon, and the crowing of a boy shall not hereby be distinquished from the crowing of a Cock;—to the taste, sometimes Sweet things prove bitter, and sometimes all things are Insipid and without Relish; and in like manner the other externals do delude us, and thus likewise it is as to the Internal Sense,—to a vertiginous person all things seem to go round, and to one drunken things appear double & now in that these senses do so oft deceive, common reason does tell us that it is prudence at all times to suspect them and not hastily to give credit thereto.
¶ That this rule as also the first do concern us, when searching after truth, and not when we are about the common actions of life; for when a friend Invites me to a glass of White wine & has given me the glasse, it would be ridiculous for me to doubt about it and to doubt its being white wine, bec: that it is possible that it may prove cider.—So (as to this Rule) if a friend gives me a shilling and it appears to the eye to be Silver there is Sufficient ground for my faith without bending the Shilling or rubbing it and the like:
Note further, that this rule dos not absolutely exclude the help of the Senses in searching for truth, but dos only intend that in themselves they are unfit to discover that which is truth; for altho the senses may teach us that things are, or that bodies do exist, as also sometimes what bodies are or what their nature and qualities are, yet it is by accident and might have been otherwise; the reason of which is bec: the mediums that Intervene sense and the object are very variable and obnoxious to changes: Hence it is, that the stars which now seem red, shall at another time seem only Redish, and at another time altogether pale or of a Whitish colour.
The Third Rule of Truth.
What ever we perceive, we perceive only by the mind. Since neither divine Revelation nor humane traditions take place in philosophy, and (according to the preceeding rule) the senses are all deceitfull, it follows that the understanding must be constituted the proper searcher for truth; hereby do we find out the natures of things, and hereby do we pass Judgment on the very things according to the very attributes which agree to them:—Which is not to be understood only concerning abstracted essences or natures (as metaphysicians term them) but also concerning every particular object which affects our Senses; for it is only the mind which (by the organs) sees, hears, feels, &c.
The Fourth Rule of Truth.
That is true which we know clearly and distinctly. The only rule which we can go by in discovering truth is a clear and distinct perception, or a perception that excludes all doubt, for it is Impossible for us to err whilst we frame such Judgments concerning things as are agreeable to our clear perceptions:—Whence, that axiome is acknowledged by us as an undoubted truth. A nosse ad esse valet consequentia. [from the knowledge of a thing we may argue the essence of that thing]—We Imagine not, because we do conceive the essences of a certain thing, that therefore we may conclude that that thing does exist in nature; our meaning is, that whatever is clearly known by us certainly hath such an essence or such a nature as is in our minds: if the existence of a thing is clearly known by us, then may we conclude that this thing is existing; if the nature of the thing is only perceived, we can only argue that this thing hath such a nature or essence.
Hence, Descartes proves the existence of A deity for (says he) if because I have a clear perception of this or that thing, it follows, that all those things which I have an Idea of, do belong unto that thing, then consequently because I cannot have a clear perception of a deity unless I add existence thereto, therefore existence is essentiall to God, or (which is all one) God necessarily or Infallibly does exist:—now the Reason why we cannot conceive clearly of A Deity unless we give existence thereto, is because a Deity Implies a being having all perfections, one of which must be existence.
¶ That this rule does respect Philosophy or naturall things, And not the mysteries of faith, here divine Authority must set us down, but there we must get A clear and distinct perception, before we believe.
If we would know how we may be certain that we do clearly and distinctly perceive a thing; we must follow the method which Right Reason sets us, or not precipitate our Judgment or determine any thing before the evident truth of perception shines forth, or a perception free from all manner of doubt is obtained by us.
The Fifth Rule of Truth.
To obtain a clear and distinct perception, it conduces much that we keep in mind so accurate a scheme or Genealogy of things and modes, that by one view as it were, we may pass through the whole universe of things beginning at the most general and ending at the most speciall.
The Reason is, because hereby (when we are searching into the nature of things) we shall know what tribe or series they belong unto, how they agree with these things and disagree with those things; and also because this will help us much in Defining things, in describing them, in dividing & distributing of {them.}
The Sixth Rule of Truth.
An Idea or perception of any thing is by so much the more clear and perfect, as it Represents many parts, causes and Adjuncts of that thing.
The reason is, because from the parts we have A prospect of the whole thing:—from the causes we gather what is contained in the effect;—from the adjuncts (as complements and ornaments) the nature of the subject and it’s disposition is Apprehended, especially from proper and innate qualities or adjuncts.
The Seventh Rule of Truth.
Those things may be said to agree, which do agree in some common Idea or Respect (or those things one of which is Included in the Idea of the other those things may be said to disagree which are the objects of different Ideas (or those things one of which is not Included in the Idea of the other).
For those things only do agree which do agree either in their Genus or Species or parts or causes or effects or subjects or adjuncts or some other respect; and those things which differ in them do only disagree.
Hence distinction (or disagreement) in generall is nothing else but a diversity which we observe among beings, which diversity (to speak properly) is found only among beings that do exist:—for that which actually is not cannot be said actually to be distinquished.
The Eigth Rule of Truth.
That Idea or perception of a thing is clear & distinct which represents the thing to the mind, according to the preceding rules of truth; that is obscure & confus’d which does recede from them more or less.
For since that Idea is the clearest & most distinct which Includes least of doubt and which represents more parts of adjuncts of a thing and does separate it from other things, it follows of necessity that that perception is clear &c distinct which represents the very thing according to the preceding Rules.
The Ninth Rule of Truth.
Any one will excell in knowledge and understanding so much the more, as he gets his mind furnished with more & more perfect Idea’s.
Since every thing is manifested by its Idea, & whatsoever is known of a thing is contained in its Idea, it follows necessarily, that the fuller our minds are of idea’s, so much the larger our knowledge will be.
The Tenth Rule of Truth.
The names of things which we use in philosophizing must be clear & determin’d as to their signification; never obscure—never ambiguous.
Since the things we Interpret with our minds are delivered by extemall discourse and the cheife perfection of this discourse is plainness, hence it is necessary that we use noted words and such as are apt to express the things, and that we put distinct names upon distinct things.