Though the number of the links may be varied the Buddha attached importance to the method of concatenation and the impersonal formulation of the whole and in one passage[461] he objects to the questions, what are old age and death and who is it that has old age and death. Though the chain of causation treats of a human life, it never speaks of a person being born or growing old and Buddhaghosa[462] observes that the Wheel of existence is without known beginning, without a personal cause or passive recipient and empty with a twelvefold emptiness. It has no external cause such as Brahma or any deity “and is also wanting in any ego passively recipient of happiness and misery.”
The twelve Nidanas have passed into Buddhist art as the Wheel of Life. An ancient example of this has been discovered in the frescoes of Ajanta and modern diagrams, which represent the explanations current in mediaeval India, are still to be found in Tibet and Japan[463]. In the nave of the wheel are three female figures signifying passion, hatred and folly and in the spaces between the spokes are scenes depicting the phases of human life: round the felly runs a series of pictures representing the twelve links of the chain. The first two links are represented by a blind man or blind camel and by a potter making pots. The third, or consciousness, is an ape. Some have thought that this figure represents the evolution of mind, which begins to show itself in animals and is perfected in man. It may however refer to a simile found in the Pitakas[464] where the restless, changeable mind is compared to a monkey jumping about in a tree.