That that is is that that is not is not is that it it is

The phrase you provided seems to play with language and syntax in a complex way. It can be broken down into parts, but its meaning is not straightforward. Essentially, it includes several instances of "is" and "that," creating ambiguity. One interpretation could be that it explores the idea of existence and identity, possibly hinting at the elusive nature of understanding something’s essence or truth. It appears to challenge the listener or reader to engage in a deeper examination of language and meaning.