It's difficult to know where to place Sigmund Freud in the canon of Western thinkers.

Some critics say they know exactly where to place him: straight in the bin. From one side of the culture war trenches, Freud's ideas are viewed as emblematic of everything that's gone wrong with Western civilisation.

When today's culture warriors look back on the revolution of the 1960s — the point at which they claim the wheels of decent society began to wobble — they see a kind of pop Freudianism run amok. Reason and social order give way to primal instinctualism, social control falls prey to individual impulse, morality is unmasked as repression, suddenly everything's about sex — and sexually, anything and everything goes.

For them, this scandalous dissolution has only intensified in the decades since. Today they see rational thought subordinated to wishy-washy moral relativism and the kind of muddled permissiveness that posits gender fluidity as scientific truth, and same-sex marriage and legalised abortion as legitimate social goods.

And all of this, we're told, is what happens when you lie society on the couch, allow it to free-associate, and treat its delusions as insights. Dangerous quackery, loosed upon the world by a dangerous quack.

Freud had his patients lie down on this couch during their psychoanalysis sessions. ( Getty Images: Mondadori )

On the other hand, it's hard to dismiss completely a figure who's had such a profound influence on contemporary life. But for someone so manifestly part of the modern cultural furniture, Freud is hard to get a fix on, to articulate in terms of exactly who and what he was.

Freud himself had a very clear idea. According to Matthew Sharpe, an associate professor in philosophy at Deakin University and a Freud specialist, the good Viennese doctor saw himself as a man of science first and foremost.

"He was very keen to establish that psychoanalysis was a science, and he tried to base his theory of the mind on the most up-to-date biological theories of his day," says Sharpe.

"Freud was a man of his time, and science at the end of the 19th century had ultimate cultural credibility. So if you wanted to be taken seriously, you had to present your theories as scientific."

But not everyone endorses Freud's scientific credentials.

"Figures like Karl Popper have claimed that the idea of psychoanalysis as a science of the mind is highly contestable," says Sharpe.

"The claims that psychoanalysis makes aren't really falsifiable, because the theory is capacious enough to explain whatever behaviour presents itself to the clinician.

"A scientific theory will make risky hypotheses. Does light bend when it travels around a planet? You can test that, once you've got the relevant telescopic equipment, and it's a yes or no answer.

"But that kind of condition doesn't really apply when you have a complex human being talking to another human being in an analytic setting for between six months and 10 years."

More than a master storyteller

In some ways it might be more appropriate to see Freud as a literary figure. Certainly the Romantic authors of the earlier 19th century were psychologists before the word existed, pioneering explorers of the depths of the self, and it's not hard to discern their influence on Freud's work.

Freud was a close reader of (among others) Goethe, Schiller, Shakespeare and of course Sophocles, whose tragedy Oedipus Rex gave Freud the mythic architecture for one of his most famous — or notorious — psychoanalytic insights.

The myth of Oedipus inspired Freud's theories about how children love their parents. ( Supplied: Dallas Museum of Art )

More significantly, Freud has given us resonant narratives that stretch culturally far beyond the point where we argue the toss over whether or not they're "true".

Subconscious desire, ego, death wish, anal retentive: if you've ever used these terms — and who hasn't? — then you've referenced stories authored by Freud, stories about the human condition that have burrowed as deep into the collective unconscious (there's another one) as anything found in Shakespeare or the Bible.

To rate these stories in terms of scientific accuracy seems like a category error, in the same way that it would seem a little off to dismiss the psychological insights of a Jane Austen or an Edith Wharton on the grounds that they'd just made it all up.

Still, it's hard to imagine that Freud would nod approvingly from the grave at the notion that he was a master storyteller first and foremost. By his own account, he dealt not just in seductive fictions but in truths about the world, truths that hold up to hard intellectual scrutiny.

A philosophical sceptic

Maybe Freud was a philosopher? He was certainly philosophically literate, conversant with the thinkers of his day and directly influenced in his work by Arthur Schopenhauer and Friedrich Nietzsche.

But again, it's likely that if consulted, Freud would confess to having mixed feelings about being tagged with the P-word.

"He was sceptical about philosophy, because he thought that philosophers overvalued the power of human thought," says Sharpe.

"There are passages where Freud compares philosophical speculation to the kinds of delusions that psychotic patients form, once their relationship with ordinary reality has broken down.

"Freud says that psychotics 'love their delusions as they love themselves'. Their very identity is dependent on delusion, which enables them to function in some way.

"So when Freud says that philosophers have the same relationship to their theories, he's saying philosophers over-invest in philosophical systems that might be internally consistent, but that one struggles to connect to phenomena encountered in the external world."

In spite of all this, there's a strong — and perhaps surprising — case to be made that Freud's most fertile legacy has been a philosophical one.

Surprising, because you might expect that professional philosophers, unkindly cast as delusional psychotics, would be a bit sniffy about admitting Freud into their ranks.

But in fact Freud has been a key figure in the development of what's been dubbed the "school of suspicion" — a line of philosophical descent that originally linked Freud with Nietzsche with Karl Marx, but has since been expanded into a broader tradition connecting such later figures as Martin Heidegger, Jacques Derrida and Michel Foucault.

The "suspicion" in this formulation refers to the sceptical way in which these philosophers approach everyday meaning on the surface of things.

What's going on under the surface

Just as psychoanalysis explores the drives, wishes and fantasies that lurk beneath our conscious account of ourselves, so there is a tendency among the philosophers of suspicion to make a strong distinction between how things at first appear, and what might actually be going on under the surface.

All of which sounds innocent enough — indeed you could say that "looking beneath the surface of what appears to be the case" is a pretty standard job description for any philosopher.

But much like Freud himself, the school of suspicion has fallen foul of today's anti-postmodern culture warriors. And no single thinker personifies the issue better than Jacques Derrida, who died in 2004, and whose legacy in the notion of "deconstruction" is viewed in some quarters as nothing less than a harbinger of apocalypse.

Derrida is loathed by many critics for his belief in the flexibility of language. ( Getty Images: Raphael Gaillarde )

Deconstruction is not so much a theory as a method, an approach to interpreting texts based on the governing assumption that authors are never in full control of the meanings they produce.

Analytic philosophers generally loathe it, and according to Matthew Sharpe, for unsurprising reasons.

"No matter how hard a philosopher tries to lock down language, lock down logic and produce a failsafe, perfectly rigorous philosophical system, Derrida argues that they'll never fully succeed — because they're using language, which Derrida believes is always flexible and can never be closed down.

"And what he takes from Freud is this idea that we make more meaning than we think, and sometimes more than we like. Because what a deconstructive reading will do, is show how an author tacitly contradicts themselves on a point that they feel they're strongly in control of."

All of which is fine if we're just talking about philosophical texts. But deconstruction has a way of getting out of its box, and Derrida's claims about the instability of meaning are intended to apply to all meaning — philosophical, scientific, legal, ethical.

Fuelling the culture wars

Few outside the academy will worry about whether or not a dissertation on Kant's categorical imperative contains unintended meanings that contradict its central thesis. But people can become very upset at the notion that more widely cherished moral certainties harbour the seeds of their own dissolution.

Religious authority, which relies on the notion of access to a set of fixed, language-proof, God-endorsed truths, is an obvious target for deconstruction. And accordingly Derrida's work has been denounced in conservative theological circles as a virulent and dangerous strain of atheism.

But deconstruction ruffles secular feathers as well.

Australia's ongoing same-sex marriage debate can be seen as a battle between defenders of "traditional" marriage and those who seek to deconstruct it — that is to say, those who argue that marriage is generative of more complex, more contradictory meanings than the familiar man-plus-woman formulation allows.

In much the same way, contemporary social anxieties around transgender issues are largely the reaction to a process of deconstruction, where the simple either/or dualism of male and female is being prised apart to reveal ambiguities that challenge the whole concept of binary sex.

We seem to have come a long way from psychoanalysis, but deconstruction is — as Derrida acknowledges — thoroughly Freudian. It's a means of exploring the "unconscious" of surface phenomena, approaching even the most seemingly unarguable meanings as texts to be read, interpreted and mined for contradictions.

And as Freud applied psychoanalysis not just to neurotic individuals on couches but to all of human civilisation, so Derrida's insights have escaped from philosophy departments and can today be found roaming the cratered terrain of the culture wars.

The battles are far from over.