Jesus was talking to His trainee apostles in the Upper Room.  It was His final briefing to them before the cross, and He challenged them to believe in Him.  Of course, they had lived with Him and worked with Him, but they did not confidently know who He was.  Peter had claimed that they believed Jesus was the Holy One of God (John 6:69) but, as the cross loomed ever closer, “… they all deserted Him and fled” (Mark 14:50), and Peter swore that he did not know Jesus (Mark 14:66-72).

Jesus had previously explained to the hostile crowds, but with the disciples overhearing, that even though they were not willing to accept His divinity they should believe that He was one with the Father because of the evidence of the miracles (John 10:37-38).  Now Jesus explained to the disciples that He and the Father have a relationship with each other (John 14:9-10).  He presented His deity as a simple choice: ‘Believe what I say, or look at what I’ve done, and ask if anybody other than God could have done it’.  It is still a good question.
 
Miracles are amazing - by definition.  But miraculous signs do not give the whole story.  Although they show what was done, they cannot explain the ultimate purpose for which it was done, or the power that made it happen.  It is necessary to have an explanation in words.  That is why Jesus’ ministry was a lot of teaching punctuated by miracles.  One without the other cannot truly define what is being done, who is doing it and the purpose behind it.  In John’s Gospel there are seven miraculous signs which are explained by the seven “I AM” sayings that Jesus is ‘the Bread of Life’(John 6:35), ‘the Light of the world’ (John 8:12), ‘the Gate for the sheep’ (John 10:7), ‘the Good Shepherd’ (John 10:11), ‘the Resurrection and the Life’ (John 11:25), ‘the Way the Truth and the Life’ (John 14:6), and ‘the True Vine’ (John 15:1).
 
There is a mistaken idea that as long as we show people love they will understand the gospel.  Loving actions are very important but can never define the gospel.  Both are needed.  However, for those who have no explanation, the only questions they need to ask are, ‘Whose power has done this?’, ‘Is He able to save me?’ and ‘Is this God at work’?’  Responsible Christians will always seek to show how the Scripture explains the meaning of the sign, revealing the character of Jesus, and advertising His loving compassion and redeeming purpose.  That is our job: to explain that Jesus is the explanation for the wonderful acts of God, and ask people to put their trust in Him.