The disciples are engrossed with the thought of separation from Jesus. To Thomas, ignorance of whither Jesus is going involves ignorance of the way. “Therefore, with loving condescension the figure is taken up, and they are assured that He is Himself, if we may so speak, this distance to be traversed” (Milligan and Moulton). All along the course to the Father's house they are still with Him.
The truth
As being the perfect revelation of God the Father: combining in Himself and manifesting all divine reality, whether in the being, the law, or the character of God. He embodies what men ought to know and believe of God; what they should do as children of God, and what they should be.
The life
Not only life in the future world. He is “the principle and source of life in its temporal development and future consummation, so that whoever has not received Him into himself by faith, has become a prey to spiritual and eternal death” (Meyer). “He that believeth on the Son hath everlasting life.” Compare Col 3:4; Joh 6:50, Joh 6:51; Joh 11:25, Joh 11:26.
“I am the way, the truth, and the life. Without the way there is no going; without the truth there is no knowing; without the life there is no living. I am the way which thou shouldst pursue; the truth which thou shouldst believe; the life which thou shouldst hope for” (Thomas a Kempis, “Imitation of Christ,” iii., 56). On ζωή, life, see on Joh 1:4.