Question: Is "belief" more or less certain than "knowledge"? Several people have told me that "having a belief" is the same as "having an opinion." How does "belief" relate to "faith" and "revelation." Is there a unique "truth" that can be known about things?
Answer: Objective truth exists independently of our ability to know it. One possesses objective truth when the knowledge of a thing exists in the mind as the thing exists in reality. Even though it is possible to be wrong (i.e. to not have the truth), and possible to have a true but narrow knowledge of something (i.e. to correctly know some but not all aspects of the thing), such possibilities do not detract from objective truth or from the possibility of knowing the truth. Absolute truth -- the objectively accurate and comprehensive knowledge of all things exists in the mind of God.
Through the use of his natural reasoning powers man is capable of determining many truths about the world around him, even to the point of knowing that there is a God and a natural moral law. But, in fact, man does not always adequately strive to know about God and His laws. Often enough man is careless in using his natural reasoning powers.
There are also objective truths about God that man could never discover through his own reasoning -- the existence of the Trinity, for example -- such truths are called "mysteries." Although they might be naturally unknowable, mysteries never contradict the truths that can be known through natural reason. Indeed, all truth is part of a grand unity that never contradicts itself. (The notion that something can be true from the religious point of view but false from the scientific or philosophical point of view -- a so-called "dual truth" -- is an Islamic heresy called Averoeism, necessary to make the false teachings of Islam square with observed reality.) When the poorly educated or the overzealous claim to find contradiction between the truths of one discipline and another it is usually due to the failure to understand the differing aspects considered by each discipline. There is no conflict, for example, between chemistry and physics, although each considers atomic structure from a different point of view.
Knowing man's limitations and his carelessness, God determined many centuries ago to make the more important things about Himself and His law available to man through revelation. God did this even though man could have known some of these things through natural reason. Belief in what God has revealed is called "faith." Faith strengthens and confirms what is correctly known through natural reason -- the two cannot be at odds, for God cannot deceive. But the knowledge of faith is infinately more certain than any acquired through the use of frail human reason. Only in heaven will faith give way to a direct knowledge of God and His creation, and even then there will be no contradiction of one "truth" over another.
In stating the truths of religion there is no higher certitude than to say "I believe," for such belief is held on the basis of information received from the Highest Authority. What we know about God we have received from God Himself; through Moses and the prophets of the Old Testament, and through God Himself, Truth Incarnate, in the New. And even then. lest there be any doubt, God's truth is confirmed in us by His Spirit of Truth, the Holy Ghost.
Recognizing the limitations of the human intellect and will, and man's propensity to rationalize even the most clearly given revelation, God established the Catholic Church to preserve and teach His truth on Earth.1 The truth of the Church's teaching is guaranteed to us by our Lord Himself, either when it exercises Its ordinary magisterium through the unanimous teaching of Its bishops over time, or through the exercise of Its extraordinary magisterium in the ex cathedra pronouncemnets of the Pope or in the similar decrees of an ecumenical council. The magisterial teaching of the Church never changes, and never adds to or subtracts from the deposit of faith received from Jesus Christ.
A small part of the answer to the question at hand is that our English language is ambiguous. According to Webster's a meaning (but only the fifth most likely) for belief can be "an opinion." Statements like "I believe it will rain tonight," and "I believe the gas station is five or six blocks down the road" are tentative expressions of opinion. They convey no real conviction about the weather or the location of the gas station. But this use of the word is not the meaning that Catholics attach to it when we say "I believe...."
Many people, the victims of modern philosophies like utilitarianism, existentialism and modernism have been taught to believe that there is no singular truth about anything -- they have accepted the notion that everything is relative; that there are no absolutes. Truth and morality, to the utilitarian, consist of that which is useful. To the existentialist, truth and morality are self created through one's actions. To the modernist they are found in a consensus of how everybody feels about them. Given such an outlook, no belief could ever be more than an opinion; and certainly could not be applicable to everyone everywhere.
Such a flexible reality can be very dangerous, particularly in terms of morality. Who is to determine what is useful to whom? How can my self-created truth relate to other people's truths? How can a consensus be developed for everyone? In practice such relativism is used as a mechanism for taking advantage of the powerless, and to eliminate undesirables. Blacks, Jews, the unborn, and the handicapped -- among a myriad of others -- can all be defined out of the moral equation with one form of relativism or another.
Yet in practical matters, even those who have become confused by ideology generally conduct their affairs with the assumption that there are unambiguous truths in the world and that they can be known, at least to some degree, through human reason. They rely on practical knowledge acquired by the human race over the centuries to produce their food and clothing and shelter, to heal their ills, to transport them to work, and any numer of other things. They recognize that human knowledge, even though it is usually tentative and subject to being refined over time, is an attempt to grasp objective truths. Aristotle gave way to Newton, who in turn gave way to Einstein, who in turn …but with each refinement we all agree that we are closer to the objective truth.
Ironically, those who are relativists when it comes to belief in God or morality often display a credulous "faith" in the beliefs of the more speculative sciences. An amazing number of people insist that "evolution" is a fact rather than a theory, or that there is life on other planets because they have an equation that proves it -- in spite of the highly conjectural reasoning of the evolutionists and the extraterrestrials.
A clear understanding of the natural sciences ought both point to the existence of singular truth, and to the difficulty of discovering such truth. A basic assumption of science is that the laws of nature are the same for everyone; that, given the same conditions, any experiment can be duplicated with the same results by any observer. It does not matter whether or not the observer finds the results useful; requires no consensus of opinion, feeling, or political point of view. Provided he does nothing to change the conditions of the experiment, the results are not formed by the observers actions, but by the principles which the Creator has built into His universe.
1. Cf. Matthew xvi: 13-20; xviii: 18; xxviii: 16-20; Mark xvi: 14-18.