Truth

[Guest Sophie]

[b]What is truth?

How do we know what is true?

Is there a universal truth or is it relative?[/b]

[Laudate_Dominum]

The questions you ask are very rich indeed. I doubt I can give a satisfactory answer, but you deserve a response of some sort. I will likely end up rambling but I hope something I say is of value to you in your search for answers.

[quote][b]What is truth?[/b][/quote]
There are different senses to this word, and thus different concepts associated with it. But ultimately God is Truth.
Truth refers to reality and actuality. God is Ultimate Reality and pure Actuality.
As an "attribute" of God, Truth is one of the transcendentals: Truth, Beauty, Goodness, Unity.. These all imply one another and have no actual distinction in God but are logical distinctions in our mind due to its contingent cognitive operations. In speaking of these things as pure perfections it can be asserted that beauty is true and good and one; similarly truth is beautiful and good and without division. The good is true, beautiful, etc..
In the realm of infused contemplation and or intellection informed by supernatural virtue and Divine Love, this fact is experientially perceived. But strictly in the realm of the natural operations of our faculties, this may not be an obvious fact.
The discernment of particular, finite truths or the reasoning out of contingent truths in the realm of propositions and/or phenomenon can be a perilous thing. Even if our natural faculties were infused with supernatural gifts, and our minds were illuminated in the gift of 'contemplatio', it would be possible to err. Lies could still work to steal this gift and darken the faculties.
The process of discerning truth pertains to your second question so perhaps I will move on.

[quote][b]How do we know what is true?[/b][/quote]
The simple answer is that to know Truth (the ultimate truth that brings peace to the soul), one must know God. To know God is to know Christ. The path to truth is the contemplation of the crucified.
A more mundane discussion would delve into theories of epistemology, logic and cognitive psychology, but this would ultimately fail to get at the heart of the question. The question cannot be resolved with mere discriptions of the processes of cognition but must include a metaphysics of the objects of cognition. This is perhaps beyond the scope of this post, lest I get carried away.
However, the limited processes of learning facts about the nature of finite reality and the discernment of what is actual, is based upon the nature and structure of being and its relation, interrelation and continuity with the form and texture of the mind in all its dimensions and layers/modes of operation. Theories of logic, epistemology and branches of psychology offer descriptions of this complex with varying degrees of comprehension and penetration but in the end do not answer the fundamental question.
Questions exist in the mind because the mind (the total person really) is in a state other than perfect fulfillment. There is no ultimate fulfillment apart from God, so as long as man remains in less than total participation in the Divine Life there will be tensions in reference to the self and in relation to reality as a whole.
We tend to separate the operations of the soul into different compartments. While there is certainly validity in this it must be remembered that these distinctions are only accidental. And when approaching something as fundamental as the foundation of human knowledge, it ought to be appreciated that the dynamics of understanding are connected with and indeed one at heart with the dynamics of the will. There are discernable hierarchies in the framework of man's higher modes of operation, and in this light I should point out that while the will is capable of commanding, the perfection of the will is in obeying. What I mean by this is that the fulfillment of the will is in conformity to the Good (aka the True, Beautiful, etc). And that this conformity defines the character of the wills commands if that will can be said to have a proper ordering. Similarly the process of discerning truth involves a dialogue with being in which the intelligibility of being and experientiality is encountered in the context of a reciprocal correspondence. In the case of an encounter with truth the response takes the form of active receptivity analogous to the 'obeying' (or conforming) of the will in response to the good. Similarly, the perception of aesthetic value is a kind of mirroring to the soul, aspects of its most essential reality in such a way that, at least in the more profound and pure encounters with beauty proper, the soul is elevated and senses something of the truth and goodness of being. In the highest of natural human experiences, typically the deepest manifestations of love, one intuits in the beauty of the encounter, a glimpse of the very meaning of one's existence. (The key to the discernment of true beauty, as distinct from the merely evocative, lies in the ennobling action of aesthetic value in contrast to a typically self-oriented kind of sensible stimulation that counterfeits aesthetic experience. This is an indication of the goodness and truth of the perceived value and its finite expressiveness of the Absolute.)
My point is that if one views the quest to resolve tensions in the realm of truth, it is in the end not possible if this quest is approached by viewing the process as purely a matter of intellection isolated from the totality of the person and human experience. The faculties are one in the soul and they are entirely interrelated and therefore one's capacity to cognize a full picture of reality is conditioned upon the harmony of all the faculties. It is a fact of human psychology that one's psychological state conditions one's perceptions of reality. This is one manifestation of the fact I am trying to get at. From a bigger perspective the harmony of the whole person with the basis of the intelligibility or 'logos' of being, captured to some degree in the values that permeate and perfect our constitution, and which are finite expressions-- and really gateways (through contuition)-- to the infinite perfections of God is at the heart of a true and harmonious perception of the self and of the world.
If I may skip the remaining 55 paragraphs that I will likely write if I continue my ramble, I shall jump to my conclusion and suggest that the answer is to live the Gospel and surrender one's life and heart to Christ, Who is the Way, the Truth and the Life.

[quote][b]Is there a universal truth or is it relative?[/b][/quote]
I fear another ramble, so I will simply say that it ought to be evident in light of my previous statement, that truth is universal. Particular contingent truths of our common experience are but limited expressions of Truth in the ultimate sense. But it ought to be clear that the very concept of truth, when reflected upon, renders absurd the idea that truth is relative. The common observation is that, to say truth is relative is to put forward a universal truth; therefore there must be at least one universal truth so truth is not relative after all. In other words it is a self-contradictory or absurd statement. One ultimately denies the validity of reason and the intelligibility of being by giving assent to such a statement. There are certainly experiences and perceptions that are relative. Countless phenomenon that are relative. But they are bound together in a coherence by the fact of an over-arching intelligibility and integrity.