Doctrines of logical quality are an attempt to answer the question: "How many qualitatively different ways are there of saying something?"
Since Frege, the normal answer in the West, is only one, assertion, but what is said, the content of the claim, can vary.
[3] Gentzen's notation definitely assimilates denial to assertion of negation, but might not quite have a single logical quality, see below.
Logicians in the western traditions have often expressed belief in some other logical quality besides affirmation and denial.
Sextus Empiricus, in the 2nd or 3rd century CE, argued for the existence of "nonassertive" statements, which indicate suspension of judgment by refusing to affirm or deny anything.
[4] Pseudo-Dionysius the Areopagite in the 6th century, argued for the existence of "non-privatives", which transcend both affirmation and denial.
[5] For Kant every judgment takes one of three possible logical qualities, Affirmative, Negative or Infinite.
[6] Hegel follows Kant in insisting that, at least transcendentally, affirmation and negation are not enough but require a third logical quality sublating them both.