Janice Turner in the Times considers knowing and not knowing. Albert Speer claimed not to know about the fate of all those evacuated Jews, but eventually he admitted “sensing” it.

[Gitta] Sereny replies: “You say you sensed something. But you cannot ‘sense’ in a void; ‘sensing’ is an inner realisation of knowledge. Basically if you ‘sensed’ then you knew.” Speer shakes his head and thanks God that Gitta was not prosecuting him at Nuremberg.

The same applies to that much-abused word “intuition.” Intuition is based on what we know, but in such a way that the specific sources aren’t clear to us. “Educated guess” is a much better way of saying it. Sereny is so right that you can’t “sense” (or intuit or make an educated guess) in a void.

What is knowing, how do we know, how do others know, how do we know how they know.

When the horrifying scope of Jimmy Savile’s crimes was exposed I asked a former tabloid executive, a long-time trader in kiss-and-tells, if he’d ever heard rumours. Well, he said, the occasional young woman would pitch up claiming Savile had molested her, without proof, so she was sent away. But, no, he didn’t know. What about those girls? He bristled: look, nobody knew.

Jesus. Says it all, doesn’t it. “We were told, repeatedly, but no, we didn’t know.”

Mind you, I can see how it happens. People say things; people quarrel with each other; work life inevitably involves clashes; it’s not always wise to take every claim as entirely true and accurate.

But at the same time – people with less power are less believed than people with more. Male producers have more power than young female employees; it’s not always wise to ignore every claim, either.

Knowing is a strange business. You can “know” and yet not know. Evidence of dark deeds may present itself, dance right across your path, be the source of gossip and in-jokes; become so enmeshed in everyday life it sets the protocols by which people work. Yet when a scandal breaks people still cover their mouths and cry “Who knew?”

The fact that Weinstein was a running joke was very telling. Then again I think I read (I can’t remember where) that Seth MacFarlane’s “joke” about not having to pretend to be attracted to Weinstein wasn’t a joke but an angry pretend-joke, because MacFarlane knew one of Weinstein’s victims and was in fact angry.

Quentin Tarantino, whose career as a director was made by Harvey Weinstein, has said: “I knew enough to do more than I did. I didn’t take responsibility for what I heard.” No kidding. Not from second-hand rumours either. His drinking buddy Weinstein was preying upon his then girlfriend, Mira Sorvino, and she told him about the hotel room assaults. But Tarantino filed them under an infatuation, “a Svengali thing”, a “1950s secretary being chased around her desk by her boss” jape.

There are plenty of people – men and anti-feminist women – who think we should go on filing such things that way.

In her fascinating book Wilful Blindness: Why We Ignore the Obvious at our Peril, Margaret Heffernan examines the prevalence of this mindset. In law, wilful blindness is information you could know, should know, but have chosen not to know. This principle means that if stopped at an airport with a suitcase full of heroin it is no defence to say that you did not look inside. Wilful blindness, Heffernan argues, is how an affair can remain unacknowledged for years, why US troops in Iraq were silent about human rights violations in Abu Ghraib, how the Catholic Church concealed endemic child abuse, why Enron bankers or those flogging sub-prime mortgages did not confront the financial apocalypse they sensed was looming. It was easier not to “know”.

There’s the bystander effect, and groupthink, and all that. It can be damn difficult to be the only one making a fuss. That’s one reason journalists are so useful: making a fuss is what they do. Janice has experience of that.

In Britain, there is no better example of wilful blindness than the Rotherham sex abuse scandal. Jayne Senior, the youth worker who blew the whistle, spent years listening to victims, collating reports. But as she shoved this material in the faces of councillors, police and social services, it was as though she was invisible. They simply refused to know.

Denis MacShane, MP for Rotherham for 18 years, throughout the reign of the grooming gangs, has always maintained he knew nothing about the 1,400 victims. But he does not refute that on March 24, 2006 he attended a conference in Rotherham hosted by Jayne Senior called Every Child Matters where she and other experts gave presentations about the crimes. Indeed MacShane made a speech! Yet after my Times interview with Senior was published, he summoned me to his house to swear on his life that right until it broke he had no knowledge of the scandal. What about that conference? It was just another constituency event. So many, they blur into one. He repeated over and over: he did not know.

It’s the same with Irish industrial schools and Magdalen laundries: people knew but they didn’t know.