Hildegard writes about how she kept her visions quiet and had doubts about their validity until she was forty years of age She had to be very careful in seeking the official assurance of others that she should proceed with recording them and painting them. And if the Church authorities had not ruled that her visions acceptable, we might never have heard of her. Her caution is a reminder that mystical experiences are not always safe to proclaim in the face of institutionalized authority with a stake in the interpretation of particular doctrines.

Her scientific views were derived from the ancient Greek cosmology of the four elements-fire, air, water, and earth-with their complementary qualities of heat, dryness, moisture, and cold, and the corresponding four humours in the body - choler (yellow bile), blood, phlegm, and melancholy (black bile). Human constitution was based on the preponderance of one or two of the humours.

Indeed, we still use words "choleric" "sanguine" "phlegmatic" and "melancholy" to describe personalities. Sickness upset the delicate balance of the humours, and only consuming the right plant or animal which had that quality you were missing, could restore the healthy balance to the body. That is why in giving descriptions of plants, trees, birds, animals, stones, Hildegard is mostly concerned in describing that object's quality and giving its medicinal use. Thus, "Reyan (tansy) is hot and a little damp and is good against all superfluous flowing humours and whoever suffers from catarrh and has a cough, let him eat tansy. It will bind humors so that they do not overflow, and thus will lessen."