Hellen Keller, a woman born blind, was asked what one sense she'd most want, and she replied "hearing", because, she said, "if I can hear, then I can see." Jesus' point in this parable is that it is in "hearing" the Word that we can begin to "see" the kingdom of God. He's not just talking about simple hearing (as in church on Sundays), but as our hearing becomes obeying. The question Jesus asks the crowd, the disciples, and us, is what type of soil are you? It will make the difference as to whether or not you receive the kingdom as a productive disciple.
Scripture: Mark 4:1-20