The penis is a means of making contact, literally "reaching out" for the other, not to hurt or invade, but to pleasure and delight – mutually! . . . Not just me, and not just the other, but both simultaneously. Is that not an ideal metaphor for what all human relationships should be?
See also the previous posts:
Not a Weapon or a Mere Tool | Body and Soul | Phallus | Penis | Hard | Soft