Besides this, the cross is a natural sign that man has always made from his artistic or from his reasoning faculty. It is the nature of light to spread rays, especially when the light is in its perfection. For instance, sometimes by looking at the sun -- at the setting sun in particular -- one Finds lines forming on the sky and on the earth: first there is one straight line and if one watches that first line minutely a horizontal line develops out of it. By keen observation of light one can find that it is in the nature of light to form one perpendicular and one horizontal line. If it is the nature of the external light to form a cross it is also the nature of the inner light: the external light is the reflection of the inner light, and it is the nature of the inner light that is expressed in the outer light. So one can see that not only the inner light is manifest in the outer light, but that the outer light is the picture of the inner light.