Christians Cannot Go to the World of Unbelievers for Truth

Eph 4:17  Now this I say and testify in the Lord, that you must no longer walk as the Gentiles do, in the futility of their minds.
Eph 4:18  They are darkened in their understanding, alienated from the life of God because of the ignorance that is in them, due to their hardness of heart. 
Eph 4:19  They have become callous and have given themselves up to sensuality, greedy to practice every kind of impurity.
Eph 4:20  But that is not the way you learned Christ!—
Eph 4:21  assuming that you have heard about him and were taught in him, as the truth is in Jesus,

On Eph. 4:17-21- this is why Christians cannot go to the world for truth. There is no such thing as "truth in everything". Truth is alone in  Christ Jesus, the Author of Truth. In light of recent events, this needs to be understood and believed by true Christians (we are separate from the world & it's philosophies and ways of life).

Gentiles. All ungodly, unregenerate pagans (cf. 1 Thess. 4:5, which defines them). the futility of their minds. First, unbelievers are intellectually unproductive. As far as spiritual and moral issues are concerned, their rational processes are distorted and inadequate, inevitably failing to produce godly understanding or moral living. Their life is empty, vain, and without meaning (cf. Rom. 1:21–28; 1 Cor. 2:14; Col. 2:18).
Eph. 4:18 alienated from the life of God. Second, unbelievers are spiritually separated from God, thus ignorant of God's truth (1 Cor. 2:14), and their willing spiritual darkness and moral blindness is the result (cf. Rom. 1:21–24; 2 Tim. 3:7). They are blind, or "hard" like a rock.
Eph. 4:19 have become callous. Third, unbelievers are morally insensitive. As they continue to sin and turn away from God, they become still more apathetic about moral and spiritual things (cf. Rom. 1:32). sensuality... impurity. Fourth, unbelievers are behaviorally depraved (cf. Rom. 1:28). As they willingly keep succumbing to sensuality and licentiousness, they increasingly lose moral restraint, especially in the area of sexual sins. Impurity is inseparable from greediness, which is a form of idolatry (Eph. 5:5; Col. 3:5). That some souls may not reach the extremes of Eph. 4:17–19 is due only to God's common grace and the restraining influence of the Holy Spirit.
Eph. 4:20–21 learned... heard... taught. Three figurative descriptions of salvation, the new birth.
Eph. 4:21 as the truth is in Jesus. The truth about salvation leads to the fullness of truth about God, man, creation, history, life, purpose, relationships, heaven, hell, judgment, and everything else that is truly important. John summed this up in 1 John 5:20.
~John MacArthur on Eph. 4

God’s Word is living and active (Heb. 4) – it measures the thoughts and motives, it reveals sin, it exhorts, it gives light and life because it is literally from God’s mouth.

So Truth is in Christ and from Christ and teaches us who He is, how to be saved, and how to live as Christians. Godliness necessarily means separation from the world.

The world cannot help us grow in Christ and in true knowledge and wisdom, which is ONLY from the God of Truth (HE tells us what reality is). Evolution and psychology are futile, hostile, dark, ignorant, alienated from God, and of calloused hard hearts. To adopt these views in anyway is sinful and adulterous.

Jas 4:4  You adulterous people! Do you not know that friendship with the world is enmity with God? Therefore whoever wishes to be a friend of the world makes himself an enemy of God.

Jas 3:13  Who is wise and understanding among you? By his good conduct let him show his works in the meekness of wisdom.

Jas 3:14  But if you have bitter jealousy and selfish ambition in your hearts, do not boast and be false to the truth.

Jas 3:15  This is not the wisdom that comes down from above, but is earthly, unspiritual, demonic.

Jas 3:16  For where jealousy and selfish ambition exist, there will be disorder and every vile practice.

Jas 3:17  But the wisdom from above is first pure, then peaceable, gentle, open to reason, full of mercy and good fruits, impartial and sincere.

Jas 3:18  And a harvest of righteousness is sown in peace by those who make peace.

Joh 3:30  He must increase, but I must decrease."

Rom 12:2  Do not be conformed to this world, but be transformed by the renewal of your mind, that by testing you may discern what is the will of God, what is good and acceptable and perfect.

Rom 12:3  For by the grace given to me I say to everyone among you not to think of himself more highly than he ought to think, but to think with sober judgment, each according to the measure of faith that God has assigned