In his new book, "The Internet of Us: Knowing More and Understanding Less in the Age of Big Data," philosophy professor Michael P. Lynch argues that the vast majority of people still fail to grasp the true importance of privacy.

Mr. Lynch, who teaches at the University of Connecticut, says privacy is a critical component in society because it is essential for respecting autonomy. Without privacy, he says, individuals lack the ability to freely make their own decisions, and therefore are stripped of a core value in a free and democratic society.

I recently spoke with him about the core reasons privacy invasions are harmful. Edited excerpts follow.

Selinger: What’s the "The Internet of Us" about?

Lynch: It's about knowledge in the Information Age – in particular, the philosophical problems that arise due to the pervasiveness and power of information technology. We often hear that we live in a new knowledge economy now, and that's clearly true in many ways: thanks to the digital devices we carry in our pockets, how we acquire, distribute and produce knowledge has changed.

But what sort of knowledge should we be acquiring and what sort of knowledge should we be producing? Those are the hard questions. The gap between what we're actually doing and what we should be doing forms the critical, and often ethical, parts of the book.

Selinger: What’s wrong with information technology?

Lynch: In itself, nothing. Information technology allows us to know more about the world than ever before. But it also allows the world to know more about us. The Internet, in other words, is a window from which we can look both ways – and from which others can, too. That's why it's so crucial to understand why privacy is important. Appropriate privacy norms tell us quite a bit about how all kinds of information should be handled.

Selinger: With so many conversations occurring today about privacy, what don’t people still understand about it?

Lynch: Lots of people don't grasp the core reasons why privacy matters. Perhaps this isn't surprising. It's fundamentally a philosophical problem. Consequently, people presume they know why privacy matters, and so readily jump to matters of figuring out how to secure it, or else combat advocates by insisting privacy protections are outweighed by tradeoffs.

But the harms that come from having your privacy unjustly invaded aren’t limited to the difficulties that many expect: consequential or instrumental matters. There’s also intrinsic harms and in-principle problems. Both matter tremendously, but can be difficult to appreciate until they’re spelled out clearly.

Selinger: So, why does privacy matter?

Lynch: Privacy matters in principle because it’s connected to the autonomy of decisionmaking. When we talk about information as private it exemplifies two different hallmarks: One is our ability to control the information and the other is our ability to protect the information from intrusion. Let’s focus on the control aspect. When I decide to share information with you or others on the Internet, this behavior tends to be thought of as an autonomous decision.

Part of the problem with privacy invasions is that they can undermine these decisions. For example, if you hacked into all the photos on my phone and shared them with your friends (who will be really bored), you’ve taken away my decision to select who to share the photos with and who to withhold them from. You’ve made that issue moot and in the process undermined my autonomy of decision. To clarify further, here’s an analogy. The situation is much like a paternalistic doctor deciding to give a patient a drug without asking for permission. The doctor makes a decision on behalf of another, removing that person out of the decisionmaking process.

Selinger: In the case of the phone hack, one reason you’d be upset is that people might somehow be able to use your photos against you. But what about people who could never exploit, extort, harass you with this data and the knowledge it conveys? On this topic, you’ve proposed a thought experiment about telepathic Martians who can read our minds but will never ever interact with any earthlings. Given their practical impotence, are these extraterrestrials committing privacy invasions?

Lynch: Let’s start closer to home and then consider the thought experiment. Imagine someone reads your e-mails but opts to never to do anything with that information. You never find out about the incident and nothing bad ever happens as a result. Has a harm been committed? Yes. We can see that this person superseded part of your autonomy. They abused their power by taking you out of the decisionmaking equation.

The same goes with the people on the faraway planet. They have taken power from us, and this matters because autonomy enables us to shape our own decisions and make ones that are in line with our deepest preferences and convictions. Autonomy lies at the heart of our humanity.

Selinger: Are you saying that having access to someone’s private information without their permission is itself a deprivation of their autonomy, and that it’s the type of deprivation which makes for an asymmetric exercise in power?

Michael: That would be precisely how I’d put it. That said, let me be clear that someone who accesses your information without your permission and doesn’t do anything about it is violating your privacy less than someone who takes the information and causes negative consequential outcomes, like reputational damage. And yet – and this is the key point – the moral residue of autonomy lies at the basis of all privacy violations.

Selinger: Is this a fundamentally existential view? Would you object to someone taking a picture of a wild animal and posting it on the Internet without its permission?

Lynch: I’d be fine with that. But there are gray areas, like parents posting photos of their kids online without asking for permission. As my daughter grows older, my wife and I have started letting her determine when a photograph is appropriate to post. This is because we believe that as children become older they become more autonomous.

Selinger: To put this in the grandest way possible, does this mean the deprivation of our autonomy in the Digital Age is a divestment in our humanity?

Lynch: Yes, although, of course, it depends on how technology is used. Plenty of digital technology improves the quality of our lives. But the privacy violations we’ve been discussing do indeed erode our humanity.

Selinger: And to put this in the most practical way possible, what are the policy implications of your view?

Lynch: Well, the first thing is to recognize that laws protecting citizens' information privacy aren’t there just to protect those citizens from the criminal misuse of their data – just as laws promoting informed consent in healthcare aren’t there to just protect us from the misuse of drugs or other treatments.

In both cases such protections are an important part of the story, but not the only part. And that means our policies – legal or otherwise – need to be crafted to recognize that in both cases, we are also protecting a citizen's basic right to autonomy. That means that governments and companies have a pretty high bar if they are going to argue that it is justified in certain cases to violate our privacy. This is a point we need to start recognizing should apply universally to information privacy.

Evan Selinger is a professor of philosophy at Rochester Institute of Technology. Follow him on Twitter @EvanSelinger.