I thought this sutta might be helpful.
Taken from access to insight:
ยง 44. {Iti 2.17; Iti 38}
[Alternate translation: Ireland]
This was said by the Blessed One, said by the Arahant, so I have heard: "Monks, there are these two forms of the Unbinding property. Which two? The Unbinding property with fuel remaining, & the Unbinding property with no fuel remaining.
And what is the Unbinding property with fuel remaining? There is the case where a monk is an arahant whose fermentations have ended, who has reached fulfillment, finished the task, laid down the burden, attained the true goal, ended the fetter of becoming, and is released through right gnosis. His five sense faculties still remain and, owing to their being intact, he is cognizant of the agreeable & the disagreeable, and is sensitive to pleasure & pain. His ending of passion, aversion, & delusion is termed the Unbinding property with fuel remaining.[1]
And what is the Unbinding property with no fuel remaining? There is the case where a monk is an arahant whose fermentations have ended, who has reached fulfillment, finished the task, laid down the burden, attained the true goal, ended the fetter of becoming, and is released through right gnosis. For him, all that is sensed, being unrelished, will grow cold right here. This is termed the Unbinding property with no fuel remaining."[2]
These two proclaimed
by the one with vision,
Unbinding properties the one independent,
the one who is Such:[3]
one property, here in this life
with fuel remaining
from the destruction
of the guide to becoming,
and that with no fuel remaining,
after this life,
in which all becoming
totally ceases.
Those who know
this state uncompounded,
their minds released
through the destruction
of the guide to becoming,
they, attaining the Teaching's core,
pleased with ending,
have abandoned all becoming:
they, the Such.
Notes
1, 2.
With fuel remaining (sa-upadisesa) and with no fuel remaining (anupadisesa): The analogy here is to a fire. In the first case, the flames are out, but the embers are still glowing. In the second, the fire is so thoroughly out that the embers have grown cold. The "fuel" here is the five aggregates (see the Glossary). While the arahant is still alive, he/she still experiences the five aggregates, but they do not burn with the fires of passion, aversion, or delusion. When the arahant passes away, there is no longer any experience of aggregates here or anywhere else. For a discussion of this point, see The Mind Like Fire Unbound, pp. 21-37.
3.
Such (tadi): An adjective to describe one who has attained the goal. It indicates that the person's state is undefinable and not subject to change or influence of any sort.
Also, I do not believe it is relevant whether or not one believe's a teacher to be an arahant. What matters is that their advice/guidance constantly is confirmed by one's experience. Whether or not Jeffrey Brook's teachings are true does not depend on him being fully enlightened, rather it depends on reality. I think the focus should be on using the things he teaches as tools, truly trying them out. If they don't work, toss them out! If they do work, continue investigating. One can discover the truth this way without needing any sort of blind faith.
That being said I am quite certain he has some high level of attainment, if not full enlightenment since his descriptions seem to precisely confirm my experience.
