1 John 1:1-4 describes well the relationship and passion of the disciples/apostles to Jesus, the Word of Life.
It so aptly describes that which they heard, seen, looked at, and touched.
To hear would not have been enough. To have seen was more compelling. But to have TOUCHED was the conclusive proof of material reality, that the Word became “flesh, and lived for a while among us.” This word “touched” (epselaphesan), the climax of the four relative clauses, describes more than a momentary contact. It means to grope or feel after to find, like a blind man in the dark.
The conclusion: the disciples (and John in particular) REALLY KNEW JESUS.