The secret of what we call omen is to be found in the law of impressions. For instance there is a belief that if you are going to do something, if a cat crosses your way you meet with ill-luck. It is easy to understand. In the first place the swift action of the cat makes a great impression upon a person; it forms a line before you, a line of action, and that line impressed upon you gives you the thought of a cross. You are intending to go straight, and your line is crossed by a horizontal action against your vertical action, which means in action one's hands nailed and feet tied. It gives the picture of the idea.