"The fear of the LORD is the beginning of knowledge," according to Prov. 1:7. In the Bible, knowledge, wisdom, and understanding are linked. They lead to each other. If you know things, you can be wise with that knowledge, understand it, and use it to the best means and ends. We are to increase in our knowledge of the Lord.
Jesus claimed to come to bear witness of the truth and that those who belong to the truth will listen to Him (John 18:37) and even said He is the epitome of truth itself: "I am the way, the truth, and the life..." (John 14:6). Grace and truth came through Jesus Christ (John 1:7). Because of Christ, we have universal, objective, transcendent, absolute, and timeless truth to live by.
One must ultimately ask: on what basis do you define or reckon knowledge? It cannot always be certain but must be true to the best possible proof and belief. Without reference to God, can there be any real knowledge? Can you make truth claims when the God of truth doesn’t exist and you deny absolute truth? Knowledge must be accepted and believed! Denying knowledge is denying reality in a way as is not knowing the truth and inventing your own truth.All in all, one must be justified to believe in knowledge. But what we now have in a secular society is a way to be intellectually fulfilled and have the answers without God in the metric especially by appealing to evolution or saying that science is the answer; au contraire, God is the only Answerer!
The starting point as far as the world or secular society (Secular Humanism) is concerned is mankind as the "measure of all things" or reference point. They believe in commencing with man and contemplating, understanding, and explaining or explaining away God! Athanasius said that the only system of thought God will fit into is the one where He is the starting point: we begin with God and explain reality or the world, not vice versa.
Reality has to correspond with the truth and if Christianity is true, then its concept of reality is worth studying and living by. If not, then it is completely irrelevant. Postmodern philosophy says that "God is dead" and this means God is no longer relevant, meaningful, necessary, or helpful in understanding reality and the world; they only want to believe what science can prove as absolute truths and not what God reveals.
This is a philosophy and not science and should be called "scientism." That is very apparent when people harness science for unscientific reasons such as making philosophical proclamations as Carl Sagan said, "The Cosmos is all that is or ever was or ever will be." Science cannot know this and this statement cannot be subject to the scientific method. Science is not the only means of gaining absolute or perfect knowledge.
The point is that without God, we can know nothing at all, we need an infinite reference to understand a finite reference point! For instance, if there is no God, life has no ultimate meaning and unless there is a God, all things are up for grabs and all things are permissible because we have no reason to believe in morals at all except for selfish preservation like a survival instinct. To have firm branches, we need firm roots and our worldview is like our roots! It is the foundation that our knowledge depends upon!
Because of God, we can say that we can know things for certain (we have a firm foundation) and that morals are absolute and not relevant to the person or situation. When you say that truth itself is relative, is that statement relative? When you say that you must not believe anything someone tells you about God, should we believe that person? When you say that you can know nothing for certain, can we trust that person is certain, and can he be certain? Soli Deo Gloria!