That is not true and I am surprised to hear a Catholic making that claim. Are you honestly trying to say that the only way that you will know that you are receiving the living Christ is by taste?
Or is it a claim of empiricism, where our knowledge of what the Reality of the Eucharist is come from the visual form of reading the Catechism or by the audial form of hearing instruction on the subject?
The former would be incorrect, as it is strictly the accidental properties that one is experiencing. The latter would be a valid claim
And the fact remains, by the definition of ‘sign’, we are called to move past and to focus on the reality. The example of St. Thomas is relevant here. He needed the sign to believe in the Resurrection. Once the sign was recognized and it pointed to the reality of the Resurrection, St. Thomas no longer needed it. We are called to do the same.
I’m sorry for the confusion in my post, I was a little tired at the time.
If by ‘know’ you mean have certainty, then of course it is not through the accidents of the bread and wine that remain. Following St Thomas I was using ‘know’ in a more restricted
sense. As St Thomas says, I don’t have the quote with me right now, while there are many things people can reason to, there are other truths that people simply would never
be able to know in this world if God had not chosen to reveal them. Because of this I
would say that it is impossible to know in this life (ie have certitude through reason) that
Christ is present in the Euharist. We have certitude, but not knowledge.
To be honest I did not intend the bolded example to signify the sign which the accidents
of bread and wine present… I recognize, looking back on it that my post was actually quite
disconnected… Maybe that will be a lesson to me, don’t post when tired!

The point I was trying to emphasize is the importance of sensible signs not just for learning a fact, but
for the constant reminder of that fact. Yes, signs are important for the sake of learning
something, but they are also important as reminders, to continuously call to mind the
reality with which we are faced. I think the use of religious pictures is a very good example
of what I’m talking about, people look at these pictures while they pray to help remove
distractions by having the pictures give them a visual reminder of who they are praying to.
I hope this clears up the misunderstanding!
EDIT: I just realized how far off topic this got, if you want to keep discussing the issue of the role of a sign maybe we should stet a new thread?]