Electricity...

Electricity: By merely looking at two wires, one of which is electrified, we can never determine which of them has an electric current. We can only discover the existence of this current from the effect of electricity, e.g., a lamp being lit. So electricity is something which exists although our eyes cannot directly see it. Gravity: If you let go of the book which you now have in your hand, it will fall to the ground, i.e., the ground will pull the book towards itself.

This power is something which we do not directly perceive through our senses. Gravitation is again one of those things which is not visible, but we come to know its existence by observing its effect: the falling of bodies to the ground. Magnetism: When we place a magnet beside a piece of iron, we do not see anything except the two objects. But when the iron is pulled towards the magnet, we discover that magnetism exists around the magnet.

Invisible Radiation: If we shine white sunlight through a prism we see on the other side of the crystal six colours (the spectrum) which are: red, orange, yellow, green, blue and violet. No more colours are to be seen on both extremes of the spectrum. However, scientists have discovered that in the place where the eyes see no more light, further ‘colours’ exist which have heating and chemical properties. These lights' are called infra-red and ultra-violet.

Intelligence & Mental Image: All of us are aware of ourselves, i.e., we perceive that we exist; and we also arrive at concepts in a gradual manner concerning matters outside ourselves which we explain by this kind of statement: "I solved the most difficult mathematical problem." Also, man is aware of his own knowledge: he knows that he knows. Intelligence is not something visible or audible in the sense that man can see it with his eyes or hear it with his ears; but everyone finds it in himself.

Others cannot learn about my intelligence through the five senses, but they can deduce its presence from the effect it produces. For example, when a scientist is expounding on a problem, it becomes clear that he has understood it.

People can construct in their own minds any form that they wish, e.g., a tower similar to the Eiffel Tower whose construction in the external world required many years, a thousand sorts of different building materials and substances, and hundreds of workers; this can be built in the mind in an instant.