But forms of knowledge that had few direct links to the senses and no connection to the immediate brought only tension to the brain, throwing the equilibrium of the whole body out of kilter: The sciences of things whose relations are difficult to grasp due to the absence of any connection with the senses, or where these relations are excessively multiplied and oblige us to make a great mental effort in our research, present the soul with a form of exercise that fatigues the inner sense on account of the over lengthy strain placed upon the brain.