Good question. I don’t know how to answer.
Well, if we can figure out Aquinas:
Question 8. The existence of God in things
Article 1. Whether God is in all things?
I answer that, God is in all things; not, indeed, as part of their
essence, nor as an
accident, but as an agent is present to that upon which it works.
For an agent must be joined to that wherein it acts immediately and touch it by its power; hence it is
proved in Phys. vii that the thing moved and the mover must be joined together. Now since
God is very being by His own
essence,
created being must be His proper effect; as to ignite is the proper effect of fire. Now
God causes this effect in things not only when they first begin to be, but as long as they are preserved in being; as light is
caused in the air by the sun as long as the air remains illuminated.
Therefore as long as a thing has being,
God must be present to it, according to its mode of being. But being is innermost in each thing and most fundamentally inherent in all things since it is
formal in respect of everything found in a thing, as was shown above (
I:7:1). Hence it must be that
God is in all things, and innermostly.
Is God in all things? Is God everywhere? Is God everywhere by essence, power, and presence? Does it belong to God alone to be everywhere?
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Question 76. The way in which Christ is in this sacrament
Article 1. Whether the whole Christ is contained under this sacrament?
I answer that, It is absolutely
necessary to confess according to
Catholic faith that the entire
Christ is in this
sacrament. Yet we must
know that there is something of
Christ in this
sacrament in a twofold manner: first, as it were, by the power of the sacrament; secondly, from
natural concomitance.
By the power of the
sacrament, there is under the
species of this
sacrament that into which the pre-existing
substance of the bread and wine is changed, as expressed by the words of the form, which are effective in this as in the other
sacraments; for instance, by the words: "This is My body," or, "This is My blood."
But from
natural concomitance there is also in this
sacrament that which is really united with that thing wherein the aforesaid conversion is terminated. For if any two things be really united, then wherever the one is really, there must the other also be: since things really united together are only distinguished by an operation of the
mind.
Is the whole Christ under this sacrament? Is the entire Christ under each species of the sacrament? Is the entire Christ under every part of the species? Are all the dimensions of Christ's body in this sacrament? Is the body of Christ in this sacrament locally? After the consecration, is the...
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So I think it comes down to
tangibility.
Yes God is in all things and omnipresent, "innermostly". But that is rather abstract.
In the Blessed Sacrament Christ himself becomes available to hold, see and ingest.