Jesus says He is the truth and is doing the Father's work because the Father has sent Him.
Yes, understanding what is true may come through reason and science, but more importantly, those who love the truth recognise those who speak the truth. We are influenced and guided by the testimonies of others by their words, deeds, attitudes and personal qualities. Thus, those in love find love, friends accept each other, a career is pursued, a commitment is made..., and the Word of God is discovered and received.
Therefore, Jesus speaks of the testimonies that accredit Him: His works, that is, His miracles; John the Baptist's testimony in pointing Him out as the Saviour; and the words of the Scriptures that refer to Him.
Lord God! May it please you that I grow to recognise your witnesses and to honour Jesus Christ, your Son, as You do by believing in Him and being worthy of His trust and friendship!
May the Triune God be blessed!