 The rational faculty is both theoretical and practical (al-Fārābī KS: 32–33; PR: 29–31). In its theoretical aspect, the rational faculty allows humans to attain the knowledge of things that are in a certain way and cannot be otherwise; that is, humans are not able to act upon them or alter them. For example, we cannot do anything to alter the fact that three is an odd number and four an even number (al-Fārābī SA: §7, 15–16). In contrast, in its practical aspect, the rational faculty deals with those things humans can act upon and alter. In this practical dimension, the rational faculty involves skills and calculation. Skills refer to acquired abilities for practicing activities such as carpentry, farming, medicine, or sailing, while calculation is related to those situations where we need to deliberate about something we want to do, when we want to do it, whether it is possible to do it and, if possible, how it should be done (al-Fārābī VC: 208–209; SA: §7, 15–16).