(also called Mind and Reason).— 1. A spiritual cognitive power. 2. The natural spiritual cognitive power by which human beings understand, judge, and reason. 

Agent Intellect (also called Active Intellect).— The intellect as abstracting the intelligible species from the phantasm and impressing it upon the patient intellect. As the agent intellect, the intellect is the proximate efficient cause of the concept in which human knowledge, the phantasm being the material cause, and the intelligible species being the formal cause. 

Intellectual Memory (also called Memory).— The intellect as having the power to retain that which it knows. 

Patient Intellect (also called Passive Intellect or Possible Intellect).— The intellect as receiving the intelligible content or species abstracted by the agent intellect from the phantasm.  In the act of cognition itself, it is by the possible intellect that man knows what he knows.  The term “passive intellect” is sometimes used solely to refer to the cogitative power. 

Practical Use of the Intellect.— Using the intellect to make or do something.  Perfected by the virtues of prudence and art. 

Speculative Use of the Intellect.— Using the intellect to know something without a per se intention of making or doing something. 

Three Operations of the Intellect (also called Three Acts of the Intellect, Three Acts of the Mind, or Three Operations of the Mind).— Understanding, judgment, reasoning.  In moral-practical reasoning, the intellect also commands.