The Church of Christ is continually represented under the figure of an army; yet its Captain is the Prince of Peace; its object is the establishment of peace, and its soldiers are men of a peaceful disposition.  the spirit of war is at the extremely opposite point to the spirit of the gospel.

Yet nevertheless, the church on earth has, and until the second advent must be, the church militant, the church armed, the church warring, the church conquering.  And how is this? 

It is the very order of things that so it must be.  Truth could not be truth in this world if it were not a warring thing, and we should at once suspect that it were not true if error were friends with it.  the spotless purity of truth must always be at war with the blackness of heresy and lies.

--C.H. Spurgeon (v).

...God and truth are inseparable...That is why God incarnate--Jesus Christ--is called the truth (Jn 14:6).

That is also way it is not particularly surprising when someone who repudiates God rejects His truth as well.  If a person can't tolerate the thought of God, there is simply no comfortable place for the concept of truth in that person's worldview, either.  So the consistent atheist, agnostic, or idolater might as well hate the very idea of truth.  After all, to reject God is to reject the Giver of all truth, the final Judge of what really is true, and the very essence and embodiment of truth itself...

[T]hat is precisely the conclusion at which many in the academic and philosophical realms have now arrived.  They no longer believe in truth as a sure and knowable reality.  Make no mistake:  unbelief is the seed of that opinion.   The contemporary aversion to truth is simply a natural expression of fallen humanity's innate hostility toward God (Rom 8:7)...[A] majority of Americans claim to believe in the God of the bible, yet still they say they are comfortably uncertain about what is true...The twin problems of uncertainty and apathy about the truth are epidemic...(pg. xvi).

[D]efining truth in biblical terms[:]...every attempt to define truth in nonbiblical terms has ultimately failed.  That is because God is the source of all that exists (Rom 11:36).  He alone defines and delimits what is true.  He is also the ultimate revealer of all truth.  Every truth revealed in nature was authored by Him (Ps 19:1-6); and some of it is His own self-revelation (Rom 1:20).  He gave us minds and consciences to perceive the truth and comprehend right from wrong, and He even wired us with a fundamental understanding of His law written on our hearts (Rom 2:14-15).  On top of all that, He gave us the perfect, infallible truth of Scripture (Ps 19:7-11), which is sufficient revelation of everything that pertains to life and godliness (2 Tim 3:15-17; 2 Pet 1:3), in order to lead us to Him as Savior and Lord.  Finally, He sent Christ, the very embodiment of truth itself, as the culmination of divine revelation (Heb 1:1-3).  the ultimate reason for all of this was for God to reveal Himself to His creatures (Eze 38:23). Pg. xviii-xix...Scripture describes all authentic Christians as those who know the truth and have been liberated by it (Jn 8:32). They believe it with a whole heart (2 Thes 2:13).  They obey the truth through the Spirit of God (1 Pet 1:22).  and they have received a fervent love for the truth through the gracious work of God in their hearts (2 Thes 2:10).  According to the Bible, then, you haven't really grasped the truth at all if there is no sense in which you know it, believe it, submit to it, and love it...

Speaking plainly:  if you are one of those who questions whether truth is really important, please don't call your belief system "Christianity," because that is not what it is (pg. xix-xx)...

Our duty is to conform all our thoughts to the truth (Ps 19:14); we are not entitled to redefine "truth" to fit our own personal viewpoints, preferences, or desires.  We must not ignore or discard selected truths just because we might find them hard to receive or difficult to fathom.  Above all, we can't get apathetic or lazy about the truth when the price of understanding or defending the truth turns out to be demanding or costly.  Such a self-willed approach to the truth is tantamount to usurping God (Ps 12:4).  People who take that route guarantee their own destruction (Rom 2:8-9).

Moreover, God has revealed Himself and His truth with sufficient clarity...[T]he cardinal truths concerning God, His power, His glory, and His righteousness are naturally known to all people through creation and conscience (Rom 1:19-20; 2:14-16).  that truth is adequately clear and sufficient to leave the entire human race "without excuse" (Rom 1:20).  All those who are condemned in the final judgment will be held responsible for rejecting whatever truth was available to them...[God] has made the truth sufficiently clear for us.  To claim that the Bible is not sufficiently clear is to assault God's own wisdom and integrity...

As always, a war is being waged against the truth.  We are on one side or the other.  there is no middle ground--no safe zone for the uncommitted...

[I]n every generation the battle for the truth has proved ultimately unavoidable, because the enemies of truth are relentless.  Truth is always under assault.  And it is actually a sin not to fight when vital truths are under attack (pg. xxi-xxiv)...

I find myself compelled to echo the inspired words of Jude to exhort my readers who truly love Christ:  you need to contend earnestly for the faith.  Truth is under heavy attack, and there are too few courageous warriors who are willing to fight...

[I]t is...important to remember why we are fighting--not merely for the thrill of vanquishing some foe or winning some argument, but for out of a genuine love for Christ, who is the living, breathing embodiment of all that we hold true and worth fighting for (pg. xxvi-xxvii)...

To suppress...truth is to dishonor God, displace His glory, and incur His wrath ([Rom 1] vv. 19-20)...[T]he Bible is the touchstone to which all truth claims should be brought and by which all other truth must finally be measured...Abandon a biblical definition of truth, and unrighteousness is the inescapable result (pg. 3-4)...

[I]n the middle of the seventeenth century, at the dawn of the so-called Enlightenment, philosophers such as Rene DesCartes and John Locke began to grapple very seriously with the question of how ewe gain knowledge.  that branch of philosophy became knows as epistemology--the study of knowledge and how human minds apprehend truth.

DesCartes was a rationalist, believing that truth is known by reason, starting with a few foundational, self-evident truths and using logical deductions to build more sophisticated structures of knowledge on that foundation.  Locke argued, instead, that the human mind begins as a blank slate and acquires knowledge purely through the senses.  (Locke's view is known as empiricism.)  Immanuel Kant demonstrated that neither logic alone nor experience alone (hence neither rationalism nor empiricism) could account for all human knowledge, and he devised a view that combined elements of rationalism and empiricism.  G.W.F. Hegel argued in turn that even Kant's view was inadequate, and he proposed a more fluid view of truth, denying that reality is a constant.  Instead, he said, what is true evolves and changes with the advancement of time.  Hegel's views opened the door to various kinds of irrationalism, represented by "modern" systems of thought ranging from the philosophies of Kierkegaard, Nietzsche, and Marx to the pragmatism of Henry James.  

Elaborate epistemologies have thus been proposed and methodically debunked one after another--like a long chain in which every link is broken.  After thousands of years, the very best of human philosophers have all utterly failed to account for truth and the origin of human knowledge apart from God.

In fact, the one most valuable lesson humanity ought to have learned from philosophy is that it is impossible to make sense of truth without acknowledging God as the necessary starting point (pg. 6-7)...

Today's philosophies are open to the notion of God without truth--or to be more accurate, personal "spirituality" in which everyone is free to create his or her own god.  Personal gods pose not threat to sinful self-will, because they suit each sinner's personal preferences anyway, and they make no demands on anyone else.

That fact underscores the true reason for every denial of truth:   "Men loved darkness rather than light, because their deeds were evil" (Jn 3:19).  Here the Lord Jesus says people reject truth (light) for reasons that are fundamentally moral, not intellectual.  Truth is clear--to clear.  It reveals and condemns sin.  Therefore, "everyone practicing evil hates the light and does not come to the light, lest his deeds should be exposed" (v. 20).  Sinners love their sin, so they flee from the light, denying that it even exists...

Modernity

Modernity, in simple terms, was characterized by the belief that truth exists and that the scientific method is the only reliable way to determine that truth...The modern mind discounted the idea of the supernatural and looked for scientific and rationalistic explanations for everything...Scientific methodologies became the chief means by which modern people sought to gain...knowledge. 

Those presuppositions have birth to Darwinism, which in turn spawned a string of humanistic ideas and worldviews.  Most prominent among them were several atheistic, rationalistic, utopian philosophies--including Marxism, fascism, socialism, communism, and theological liberalism.

Modernism's devastating repercussions were soon felt worldwide.  Various struggles between those ideologies (and others like them) dominated the twentieth century.  All failed.  After two world wars, nonstop social revolutions, civil unrest, and a long ideological cold war, modernity was declared dead by most in the academic world (pg. 7-9)...

Postmodernism

Accordingly, the new ways of thinking have been collectively nicknamed postmodern...Postmodernism in general is marked by a tendency to dismiss the possibility of any sure and settled knowledge of the truth.  Postmodernism suggests that if objective truth exists, it cannot be known objectively or with any degree of certainty...Nothing is certain, and the thoughtful person will never speak with too much conviction about anything.  Strong convictions about any point of truth are judged supremely arrogant and hopelessly naive.  Everyone is entitled to his own truth.

Postmodernism therefore has no positive agenda to assert anything as true or good.  Perhaps you have noticed that only the most heinous crimes are still seen as evil...[The] notion of evil does not fit in the postmodern scheme of things.  If we can't really know anything for certain, how can we judge anything evil? 

Therefore postmodernism's one goal and singular activity is the systematic deconstruction of every other truth claim.  The chief tools being employed to accomplish this are relativism, subjectivism, the denial of every dogma, the dissection and annihilation of every clear definition, the relentless questioning of every axiom, the undue exaltation of mystery and paradox, the deliberate exaggeration of every ambiguity, and above all the cultivation of uncertainty about everything...In the postmodern perspective, certainty is regarded as inherently arrogant, elitist, intolerant, oppressive--and therefore always wrong...From a spiritual perspective, however, the rise of postmodernism has been anything but a positive development.

Postmodernism has resulted in a widespread rejection of truth and the enshrinement of skepticism.   Postmodernists despise truth claims...

Postmodernism's preference for subjectivity over objectivity makes it inherently relativistic.  Naturally, the postmodernist recoils from absolutes and does not want to concede any truths that might seem axiomatic or self-evident...Postmodernism therefore signals a major triumph for relativism--the view that truth is not fixed and objective, but something individually determined by each person's unique, subjective perception.  All this is ultimately a vain attempt to try to eliminate morality and guilty from human life...

Postmodernists are generally suspicious of rational and logical forms.  They especially do not like to discuss truth in plain propositional terms...A proposition is an idea framed as a logical statement that affirms or denies something, and it is expressed in such a way that it must be either true or false...In other words, propositions are the simplest expressions of truth value used to express the substance of what we believe.  Postmodernism, frankly, cannot endure that kind of stark clarity...[T]o make any cogent argument against the use of propositions, a person would have to employ propositional statements!  So every argument against propositions is instantly self-defeating...    

Let's be clear:  truth certainly does entail more than bare propositions.  There is without question a personal element to the truth.  Jesus Himself made that point when He declared Himself truth incarnate.  Scripture also teaches that faith means receiving Christ for all that He is--knowing Him in a real and personal sense and being indwelt by Him--not merely assenting to a short list of disembodied truths about Him. 

So it is quite true that faith cannot be reduced to mere assent to a finite set of propositions (James 2:19)...Saving faith is more than a merely intellectual nod of approval to the bare facts of a minimalist gospel outline.  Authentic faith in Christ involves love for His person and willingness to surrender to His authority.  The human heart, will, and intellect all consent in the act of faith.  In that sense, it is certainly correct, even necessary, to acknowledge that mere propositions can't do full justice to all the dimensions of truth.

On the other hand, truth simply cannot survive if stripped of propositional content.  While it is quite true that believing the truth entails more than the assent of the human intellect to certain propositions, it is equally true that authentic faith never involves anything less.  to reject the propositional content of the gospel is to forfeit saving faith, period...

Propositions force us to face facts and either affirm or deny them, and that kind of clarity simply does not play well in a postmodern culture (pg. 13-16)...

The Truth War: Fighting for Certainty in an Age of Deception by John MacArthur (Hardcover - April 3, 2007)