Scaffolding

The scaffolding was safe to use, which was a relief. There it was, crawling up all over the front and sides of the big old building. Up you could get, and up you could confidently remain. One could step with sureness onto whatever there was to be stepped onto, sure that you weren't going to come crashing.
How could you be sure? Well in the first place it looked solid enough, not that scaffolding ever looks particularly solid, but still as far as scaffolding goes it looked solid enough. But other than that, and more importantly, there was a sign, an authoritative looking one, on which was written, "Scaffolding Safe To Use."
And so a sign, and you can't go arguing with signs - or if you can it would be pointless, more in the way of a soliloquy than an argument. Interrogate all you like, all you'll get is the same monotonous statement.
But who put the sign there? Someone responsible. Yes, but who? Who is responsible? Well, whoever specifically is responsible is someone responsible, a responsible person, and by virtue of his responsibility he is responsible for ascertaining the safety of the scaffolding.
And how do we know this person is sufficiently responsible in such matters?
He has been adjudged to be so by someone else even more responsible.
So if you're going to go ascending and placing yourself atop this scaffolding, you can put your trust in how steady it all looks, the authoritativeness and accuracy of the sign, and the responsibility of those responsible for putting up the sign. You could also decide to ignore all assurances from signs and the like, and just take things in your own hands, leaving perhaps a little gathering below gathered around and debating matters.
"I don't like the look of it at all."
"Yes, but look at the sign."
"True, true, there is the sign. You can't go arguing with signs, especially ones like that."
"But who put it there?"