The phrase 'our sincerity' is correct and usable in written English.
You can use it when expressing strong and heartfelt commitment to an idea or cause. For example, "We promise to uphold the highest ethical standards in our work, with our utmost sincerity."
Our sincerity and determination would be questioned.
We want to show our sincerity.
"The North Korean leadership understands our sincerity, but they just cannot say so yet, because they must maintain control".
"We were very clear about our sincerity… we wanted very high penalties, we wanted a real disincentive for the poachers," she said.
"As cynically as the rest of this stuff is ending, it will validate the one place we put any of our sincerity, which is individual action".
"My disciplinary decision led the public to question our sincerity, our commitment, and whether we understood the toll that domestic violence inflicts on so many families.
And one of the following must be true: we (a) doubt our hosts' sincerity and suspect they do want our gifts, invites to the contrary; or (b) are so generous that we simply cannot turn up empty-handed; or (c) have all been burned at least once, just like you — the only fool who showed up giftless.
And it doesn't take Freud to see how our predilection for concealed naughtiness in the form of innuendo speaks to our fear of sincerity.
So why couldn't we speak the vocabulary of our institution with sincerity?
In this age of New Sincerity, our tendency is to view these self-directed jokes as cynicism, as a sort of qualification on the genuineness of their music.
Our vows of ceaseless sincerity rise from watching our parent's phony traditions, I suppose.
