You can't see it because it has no form. You can't hear it because it makes no sound. You can't touch it because it has no substance. It cannot be known in these ways, because it is the all-embracing oneness.
When you block a person, they can no longer invite you to a private message or post to your profile wall. Replies and comments they make will be collapsed/hidden by default. Finally, you'll never receive email notifications about content they create or likes they designate for your content.
Note: if you proceed, you will no longer be following .