In the Middle Ages no one would have ever dreamt of destroying life in order to understand it, and in ancient times any doctor would have looked on this as the height of madness. In the Middle Ages a number of people were still clairvoyant; doctors could see into a man and could discern any injury or defect in his physical body. So it was with Paracelsus, for example.
But the material culture of modern times had to come, and with it a loss of clairvoyance. We see this particularly in our scientists and doctors; and vivisection is a result of it. In this way we can come to understand it, but we should never excuse or justify it.
The consequences of a life which has been the cause of pain to others are bound to follow, and after death the vivisectionist has to endure exactly the same pains that he inflicted on animals. His soul is drawn into every pain he caused. It is no use saying that to inflict pain was not his intention, or that he did it for the sake of science or that his purpose was good. The law of spiritual life is inflexible.
Source: Rudolf Steiner – GA 95 – At the Gates of Spiritual Science: LECTURE THREE: LIFE OF THE SOUL IN KAMALOKA – Stuttgart, 24th August, 1906
Translated by E.H. Goddard & Charles Davy