It is not wrong to ask the question, "How do I know that your faith is the true way to God?"  But you need to look in the right place for the answer.  Human beings have an inbuilt desire to reach out to somebody or something bigger than themselves, believing that there is more to life than the world offers (Ecclesiastes 3:11).  So, thousands of religious ideas have been spawned as people search for an external meaning to their lives (Acts 17:24-28).

The Jews had been favoured by the revelation of God's law, but they could never keep it perfectly.  For them the presence of God was in miracles and powerful cosmic events, but people refused to receive His Word and many perished.  The Greeks were masters of logic.  Yet logic needs a starting point, and without that all logical ideas will become meaningless.  And so the trail of Christless philosophies has never been able to find God.  We must start with the unique God and accept His revelation of Himself in order to find Him and relate with Him.  

The gospel is the message of how to find God: it centres on Jesus Christ who was God in a human body (also described as the Logos or Word of God – John 1:1).  His death, by crucifixion, was God's logical way to accept responsibility for the sins of the world, satisfy His own justice, forgive sinners who repent and bring them into His family.  Yet neither the Jews nor Greeks could accept it because they refused to accept Jesus Christ … the key to God's law and logic.  What the world called foolish was actually God's wisdom.  The apparently weak Christ, who died, proved to be the strong Christ who reigns.  

The world continues to ignore the Lord Jesus Christ in its search for spiritual reality.  The road to hell is paved with good spiritual intentions.  But Jesus said that nobody can find God except through Him (John 14:6).  Meanwhile, He and His disciples are derided and persecuted.  Their faith is declared foolish and futile – while other faiths trumpet their power or their wisdom.  So do not be surprised if the world hates you (1 John 3:13) or causes you pain (1 Peter 4:12).  That does not mean you are foolish; it validates your spiritual authenticity (Matthew 10:22)!  Meanwhile keep on announcing Jesus Christ as God's wisdom for a foolish world!