These are things we cannot comprehend in our thoughts. The very thought of ‘picturing’ the concept of ex nihlo already contradicts what ex nihlo truly is. Our minds think within space/time, so our concept of eternity is false too when we try to visualize it.
If we cannot fathom these, then how can we be sure they exist?
Knowing what it is to experience something and fathoming a concept are different. We understand the passage of time as representing change. We don’t immediately know anything that is immutable, but we can to a degree understand intellectually what it is not to change. Nothing, I’d say is the greater difficulty, but not impossible.
I’m going to back up a little bit and say we understand these concepts not by immediate experience but by negation. Eternity is without change. Nothing is without being.
If you want to be a saint, WannabeSaint, you must come to know, and live in, the Truth which is not gained by any natural means, but only by gift. And this gift brings certitude “within itself” so to speak: a Self-declared truth: I AM.
“If we cannot fathom these, then how can we be sure they exist?” As Jesus said to a very educated Pharisee:
John 3:5 Jesus answered, "Truly, truly, I say to you, unless one is born of water and the Spirit, he cannot enter the kingdom of God.
John 3:6 That which is born of the flesh is flesh, and that which is born of the Spirit is spirit.
Our mind can understand immaterial concepts because the human mind is itself immaterial. The intellect is a faculty of the immaterial soul. It’s purpose is to abstract from the particular to the general. The senses gather data, the brain organizes it, the mind abstracts from data to produce ideas and concepts.
We can’t! It is as easy as that. We have no experience of nothing or eternity. Nor can we observe nothing or eternity in any way. So to claim that we somehow can conceptualize those is, in my opinion, nothing but non-verifiable word constructs.
To be able to create a sign which you say represent infinity does not mean you somehow understand infinity. Math is a language among other languages. A very powerful language indeed. But still a language.
Yet concepts such as eternity and ex-nihilo, are commonly used in theological writing, No human mind can fully comprehend the nature of God, yet God is not a non-intelligible being, We are created in his likeness, so we do have something in common, such as a non-material soul with an intellectual faculty capable of discerning truth.
Language is used to express ideas, which are in themselves non-material.
First, “to picture” is not “to understand”. Imagination is not the same thing as reason.
Second, um, why on Earth would you need to be able to imagine or comprehend things (fully in order to know they exist?
Have you tried checking if you have similar doubts in a different context?
So, let’s try an exercise.
Can you imagine an atom? A molecule? The database of this forum? Pattern of neuronal connections in your brain?
Now, what was the result? For example, for an atom, did you imagine a “planetary model” with lines for “orbits”? But then you imagined an atom badly. If that is sufficient, it is not that hard to imagine creation ex nihilo badly too (imagine an explosion in an empty space).
So, if you trust your reason (and reason of various scientists) on those matters, even when your imagination is not able to achieve much, why shouldn’t you trust your reason (and the Church, reason of various philosophers and theologians) on the matters like creation ex nihilo?
Is there any good reason to think that you should doubt existence of what you cannot see or imagine for that single reason?