Dear friend,
On the contrary, it has been my experience here that it is the people who have no theological knowledge who tend to reduce God to the limitations of their own human experience. So often I have to remind people that God is not just a bigger version of us. In creating us, God has designed us to seek him by giving us an appetite for truth. This underlies all our desire for knowledge. Certainly, ignorance is not an acceptable alternative.
Actually we can ascertain much about God by considering what he is not. This is known as the “via negativa” (the negative way). For example, we can say that God cannot by many, but only one. To have two gods, would mean that what distinguishes them from each other, means that they each lack a distinguishing feature that the other has.
We can also learn about God through analogy, by which we can compare aspects of God with things that we already know. Analogies, by their very nature, tend to limp. But while the similarities may be more incorrect than correct, they still can tell us something of God that is true.
See:
catholic.com/encyclopedia/analogy
You mention substance. Since God took on a human nature in the Person of Jesus, we use the term ‘substance’ in understanding something of the Eucharist because it has a is physical aspect as well as a spiritual one.
For more on ways of understanding God, I suggest this article by Matt Fradd:
mattfradd.com/how-to-explain-and-not-explain-the-trinity/
Fr. Vincent Serpa, O.P.
