What does “God is without passions” mean?

Most modern ears hear “without passions” as synonymous with “emotionless,” meaning something like “without feeling,” and again it’s important to understand the terminology. Both “passion” and “impassibility” are related to the word “passive.” In the tradition, “active” is the opposite of “passive;” an “agent” (cognate with “active”) is one who acts, a “patient” (cognate with “passive” and “passion”) is one who is acted upon. To be passionate in this sense is to be controlled by forces (including what we now think of as emotions) stronger than our wills; to be a patient is to be governed by the will of another. But God’s will cannot be overruled; He will not be ruled by another. To say that God is “without passion,” therefore, properly means that God is not passive, not acted upon or overruled by any other power or influence; He is the Supreme Free Agent; all of His actions are free; none of His actions is constrained.

To say that God is “without passion” should not be understood as a denial that God feels or a denial that He has emotions in something like—though also different from—our usual sense of the word. Scripture clearly affirms that God feels love, compassion, pity, hatred, and anger. Because our emotions are unreliable, inconsistent, and always affected (or infected) by our sinfulness and fallibility, our experience of emotion is only a very imperfect indicator of God’s experience. For example, when we feel hatred, it tends to overrule our feelings of love, so that we don’t fully experience both at the same time, we experience both as fluctuations, and we register our emotions as changeable.

–from a brief article by William Tate