Ultimate Things = Idols

Idols in ancient times had perceived practical purposes. One might have an idol for business, fertility, or good health. All aspects of life were viewed as having a spiritual dimension that people needed to keep in check in order to get favor from gods. When dealing with idols, we are talking about good things in life that we can make ultimate. There are many good things that eventually become bad. Think of food, or medicine, or technology that can heat our homes but can also create nuclear bombs. For some examples, see here: https://www.webmd.com/balance/ss/slideshow-too-much-good-thing.