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What is Truth? One may be sure to be certain, 1). that truth is truth and  2). NOT (~) lies (more strictly falsities), & 3). A thing is either true or false.  Trite? Not really, it is your fist example of ‘a priori’ rather than  ‘a posteriori’ reasoning in search of truth, under the laws of identity, non-contradiction & excluded middle.
1. - One might say it is a faithful correspondence of absolute integrity between a statement about something, and that something referred to, of the form, subject copula predicate , where the predicate affirms or denies something about the subject with absolute certainty of integer, integrity, fidelity, correspondence and conformity with fact or reality. 2 - A proposition (the literal meaning of an  indicative sentence, as distinct from the literal meaning of an exclamatory sentence) amounts to the first sentence 1. -) above,  being verifiable by some reasoning process. 3 - Reasoning must follow certain rules to be accepted as valid, that is to say the process involves either a).  moving in steps from a major premiss to a minor premiss, and thereafter to a conclusion, (a syllogism, a posteriori, reasoning from experience) or else b). the validity arises from a mere understanding of the meanings of the terms in the proposition. (a priori, assumed axioms, innate to thinking itself).
To tease out these ideas, the sentence “ALL unmarried men are bachelors.” is a proposition that is verifiable, whereas “Oh dear!” is not an assertion about properties of anything in particular, even its meaning is ambiguous without context.  Following the rules, if one states that John is an unmarried male, according to valid formal reasoning, the conclusion “John is a bachelor follows from the first major premiss (ALL etc)  and second (John etc, is one instance of ALL) minor premiss.  Finally, if the statement “all unmarried men are bachelors.” is comprehended in the manner it commonly is understood, then it is a truth innate to thinking, namely a priori, since no experience is required to determine its truth, the statement is true by definition, the terms unmarried men, and bachelors, are interchangeable since they have the same meanings. Whereas “John is an unmarried male” requires a determination (experience) to establish that John is unmarried and not a female. Just like “All triangles are plane rectilineal figures that have three sides whose angles add up to 180 degrees.” Where examining a figure with four sides will reveal it  belongs to the class of squares rather than triangles.
A thorough familiarity with the notions of such axioms, a priori and a posteriori type of reasoning added to which there are two essential classes of judgements, is vital for a clearer understanding of the nature of truth.
Judgements are essentially of two types, subsumption and comparison. To adjudge whether John is a bachelor, is to  determine whether ‘John’ is an instance of a case under the rule about  ‘ALL unmarried men’. If so, then John is a bachelor will be the conclusion of a subsumptive judgement.  If John is not an unmarried man, either because he is married, or he is in fact either a she or a statue, will require judgements of comparison where John’s attributes are compared with married  people, or John’s attributes are compared with  women and statues.  The concluding judgement that John is not an unmarried man, will be derived by firstly the non-identity of John’s attributes with those under the rule, and then perhaps comparisons between married people, females, or other terms, namely by comparing John, with similar entities that do not fall under the first rule, but may fall under different rules. (The law of thought, known as the law of identity).
An early example of the correspondence theory of truth:
Is found in the proposition from Aristotle, Metaphysic book IV ch 7: 1011b 26-7:
(1)To say of what is that it is not, or of what is not that it is, is false,
while to say of what is that it is, or of what is not that it is not, is true.”
Whereas a more modern version taken from Descartes understands truth, in the strict sense as:
(2) Denoting “the conformity of thought with its object
Perhaps the most recently acceptable version taken from Russell Chapter XII understands truth where:
(3) A belief is true when there is a corresponding fact, and is false when there is no corresponding fact.
Personally I am less happy with the second and third notions, than the first.
The reason is THINKING! Since, were there no thinking entities, it doesn’t follow there are no correspondences.
(and while I perceive and would posit at least 9 dimensions of reality, 3 of space, ‘width,length,height’, 3 of time, ‘past present, future’, & 3 of  thought, ‘conscious, subconscious, collective’).  For the purpose of this discourse I am concerned only with space, time and a single instance of the collective consciousness rather than subconsciousness.
Hamlet says “there is nothing either good or bad but thinking makes it so.”
It appears to me a similar statement as “there is nothing either true or false but thinking makes it so.” strikes against the heart of what we mean by truth / falsity, and makes it, like the former, a relative notion that may vary from man to man. Descarte’s thought and Russell’s belief are both introducing different senses to the essential references of ‘object’ or ‘fact’, to Aristotle’s original, which in my view requires no other qualification than ‘ceteris paribus’ (all things being equal), such as the relevant temporal aspect that could throw the entire argument into a Heraclitean fire of FLUX where only change is real, stability is illusion, and since “We both step and do not step in the same rivers twice.” ( The river is not the same after a moment in time, nor is the man), this absolute dictum by Aristotle might have no validity. But it does,  Aristotle would have known of Heraclitus’s theory, and one must give the benefit of doubt that he meant something like “to say of what is that it is at the same moment in time, is true for all or any entities capable of referring to objects.
Both Knowing and Believing belong to a separate discipline, epistemology, examined briefly in the third section of these philosophy pages.
Thus, as we have learned, True Knowledge consists of a set, of axioms that will ring true, in this world, any world, this space, any space and this or any time to any thinking entity.  Such axioms will be drawn from Logic and Mathematics. Since my particular interest is Logic, I refer the reader to the three laws of logic, which appear to me to be irrefutable, except that a logician is required to hold two opposites as consistent with the notion that either one or the other is true logically. A parallel can be drawn with this difficult proposition by referring the reader to the paradox that arises from the consequences of logical empiricism, in Aristotle’s well known paradox of the sea  battle. Two  propositions 1. There will be a sea-battle tomorrow  2. There will not be a sea-battle tomorrow. This is a complex matter to digress upon here, save to say that since the two propositions are contradictory, then according to the law of excluded middle (logic) one of the propositions (in or about the future) is true necessarily.
For me, knowledge and belief are so very distinct, where belief is subject to a protracted empirical verification process involving perceptions and sensory data, and there remain certain notions for which it appears there is no possibility of establishing any scientific methodology for such determinations. I have in mind the notion of the existence of God.
Briefly the problem of His existence has been well expounded in the ontological and cosmological arguments, but they somehow leave the latter correspondence theory indeterminate, especially when one has to consider one of the particular problems of language, namely whether existence is an attribute.
While this reveals my bias towards the Platonic distinction between Understanding and Opinion. I should point out the particular purpose of this historical explanation is to bring these concepts into the courtroom, and explain where I feel there is a serious deficiency; in my view, in testimony deposed as “I believe the above statements are true” where the deponent has committed so many serious breaches of logical reasoning as to make any testimony as to their closeness of epistemological contact with the objects of their perception, totally unreliable, and closer to fiction, than reality (as it is in the objective world).
The particular relevance of this explanation will I hope become clearer as the reader examines the priorities between testimony presented as facts, which depend on the witnesses, and their aforementioned testimony, depending on processes of reasoning, where the coherence of the whole is totally undermined by assertions that are unmistakably fallacious. It appears in many of the cases I have had the misfortune to be enjoined, that my adversary, while relying on a book of rules, will seek to get a case dismissed, for reasons that have no bearing whatsoever on the arguments themselves.
The last defendant, case Winter v Amtrak express parcels Ltd,, reveals a powerful inclination to the use of words, mendaciously and without there being the relevant charge (that positive or negative characterisation in their usage that makes the words move emotions, events and actions in the outside world). Words uttered with understanding and coined in their usage; rather than taken from a clipboard of useful phrases (without understanding them), act as touchstones to the potentialities in the minds of their recipients.
I have in mind here:  L97  <King. [Rising.]> My words fly up, my thoughts remain below:
|L98 Words without thoughts never to heaven go. (Hamlet prior to the bedroom scene)
The outcome of failing to use words with understanding, is in my view that consequence where the party so doing;
Gets lost in a sea of words, who's meanings so elude them, they eventually drown in gibberish.”
To digress to another theme of truth in court, the first priority for the claimant or defendant, whoever you may be, is to subject the other party's arguments to some tests of logic, (not particularly within the formal calculus of logic, to which the unaccustomed reader may have little familiarity) but by merely observing the consistency, and contradictory nature of a mendacious opponent, and holding these against at least the three primitive axioms of logic, expressed by the law of Contradiction, Identity and excluded middle. These three laws are explained more fully on logic section of this site, The elements of Logic, Dealing with these priorities, will reveal the design and purpose of the other party, and once that is clarified, all the other pieces of testimony will most likely fall into a schema that may be called their willful intent and teleology.
Just like the home page, the Philosophy  pages on Truth, Falsity, Free-Will, Determinism, Knowledge and Belief, plus some other very important words required for a minimal understanding of  the greatest problems Philosophy has investigated. A list of single lines showing how our greatest writers have used the terms. Guess the origin of each line?
Shakespeare on Truth
Your bait of falsehood takes this carp of truth; And thus do we of wisdom and of reach,
Doubt truth to be a liar; But never doubt I love.
The instruments of darkness tell us truths, Win us with honest trifles, to betray's
Commencing in a truth? I am Thane of Cawdor. If good, why do I yield to that suggestion
truth will come to light; murder cannot be hid long; a man's son may, but in the end truth will out.
Truth's a dog must to kennel; he must be whipp'd out, when
But she tells to your Highness simple truth! ANGELO. O peflur'd woman! They are both forsworn
Which is our honour, bitter torture shall Winnow the truth from falsehood. On, speak to him.
But for the certain knowledge of that truth I put you o'er to heaven and to my mother.
But most of all agreeing with the proclamation. LUCIO. Away; let's go learn the truth of it
Nay, it is ten times true; for truth is truth To th' end of reck'ning.
To make the truth appear where it seems hid, And hide the false seems true.
As there comes light from heaven and words from breath, As there is sense in truth and truth in virtue,
CASSIO. I pray you, sir, go forth, And give us truth who 'tis that is arrived.
Cannot a plain man live and think no harm But thus his simple truth must be abus'd With silken, sly, insinuating Jacks?
Rom. If I may trust the flattering truth of sleep My dreams presage some joyful news at hand.
And constant stars in them I read such art As truth and beauty shall together thrive
Where, as they had deliver'd, both in time, Form of the thing, each word made true and good, The apparition comes.
As I do live, my honour'd lord, 'tis true; And we did think it writ down in our duty To let you know of it.
That you have ta'en these tenders for true pay, Which are not sterling. Tender yourself more dearly,
I swear I use no art at all. That he is mad, 'tis true: 'tis true 'tis pity; And pity 'tis 'tis true. A foolish figure!
[aside] O, 'tis too true! How smart a lash that speech doth give my conscience!
How should I your true-love know From another one?
Shakespeare on False, falsely, falsity.
nor has Coriolanus Deserved this so dishonour'd rub, laid falsely I' th' plain way of his merit.
Why did you wish me milder? Would you have me False to my nature? Rather say I play The man I am.
To be more fresh, reviving. She is fool'd With a most false effect; and I the truer So to be false with her.
A father cruel and a step-dame false; A foolish suitor to a wedded lady That hath her husband banish'd.
that I have adventur'd To try your taking of a false report, which hath Honour'd with confirmation your great judgment
See you now- Your bait of falsehood takes this carp of truth; And thus do we of wisdom and of reach,
From the fair forehead of an innocent love, And sets a blister there; makes marriage vows As false as dicers' oaths.
tell them that I will not come today. Cannot, is false, and that I dare not, falser: I will not come today.
 whether thy tale be true. SALIS. As true as I believe you think them false That give you cause to prove my saying true.
Your uncle must not know but you are dead: I'll fill these dogged spies with false reports;
Three days before; but this from rumour's tongue I idly heard-if true or false I know not.
Do not prove me so. Yet I am none. Whose tongue soe'er speaks false, Not truly speaks; who speaks not truly, lies.
Since I must lose the use of all deceit? Why should I then be false, since it is true That I must die here,
Knowledge, and reason, I should be false persuaded I had daughters.
you have mighty business in hand. Corn. True or false, it hath made thee Earl of Gloucester.
do not fall in love with me, For I am falser than vows made in wine; Besides, I like you not.
Wrench awe from fools, and tie the wiser souls To thy false seeming!
'tis all as easy Falsely to take away a life true made As to put metal in restrained means To make a false one.
As for you,Say what you can: my false o'erweighs your true.
So disguise shall, by th' disguised, Pay with falsehood false exacting, And perform an old contracting.
but let your reason serve To make the truth appear where it seems hid, And hide the false seems true.
from his mouth, what he doth know Is true and false; and what he, with his oath And all probation, will make up full clear,
A goodly apple rotten at the heart. O, what a goodly outside falsehood hath!