"A true thing is true"
Of course if you make the hypothesis that the thing is true, then it's true. A "true thing" is always true..
But the hard part is not so much to understand the question, but to don't forget to question the hypothesis : this thing that's called "true thing", it's really a "true thing" ?
And even it's not really the point of the talk. Your point is clearly that a true thing is true. My point is, yes, but it's never absolutely true. Your message explain very great by itself why it isn't and why it can't be!