Idolatry need not be a cult of tangible idols.
It can also be the cult of natural forces and objects such as the sun and moon or the sea.
There can even be a cult of completely abstract entities that are perceived in the minds of believers not as material forms but as spiritual and abstract images.
At times, idolatry represents as gods those entities that are morally reprehensible.
In various creeds there were cults of gods who symbolized power, war, sex, death, and so on.
Yet even if the entity is not a negative one in itself, and even if it is a totally abstract spiritual entity, the focus on it can still be defined as idolatry.
In the more general sense, idolatry is not specifically the presence of real and concrete statues, or as the multiplicity of gods, but the creation of what the Bible calls–other gods–that is, the turning of some entity, as it were, into a supreme goal, into a god.
This is the most abstract and superior aspect of idolatry.
But this, like the material cult of idols, is in complete contradiction to the essential faith in one God.
–Rabbi Adin Steinsaltz
From We Jews by Rabbi Adin Steinsaltz