Martin Heidegger(1889-1976) was the most important and influential philosopher in the continental tradition in the 20th century. Being and Time, first published in 1927, was his magnum opus. There is no way of understanding what took place in continental philosophyafter Heidegger without coming to terms with Being and Time. Furthermore, unlike many Anglo-American philosophers, Heidegger has exerted a huge influence outside philosophy, in areas as diverse as architecture, contemporary art, social and political theory, psychotherapy, psychiatry and theology.

However, because of his political commitment to National Socialism in 1933, when he assumed the position of Rector of Freiburg University in south-western Germany, Heidegger continues to arouse controversy, polemic and much heated misunderstanding.

The hugely important matter of the relation between Heidegger and politics is the topic for another series of blogs entries. Indeed, to my mind, the nature and extent of Heidegger's involvement in National Socialism only becomes philosophically pertinent once one has begun to understand and feel the persuasive power of what takes place in his written work, especially Being and Time.

The task I have set myself in this series of blogs is to provide a taste of the latter book and hopefully some motivation to read it further and study it more deeply. But once you have read Being and Time and hopefully been compelled by it, then the question that hangs over the text, like the sword of Damocles, is the following: how could arguably the greatest philosopher of the 20th century also have been a Nazi? What does his political commitment to National Socialism, however long or short it lasted, suggest about the nature of philosophy and its risks and dangers when stepping into the political realm?

Being and Time

Being and Time is a work of considerable length (437 pages in the German original) and legendary difficulty. The difficulty is caused by the fact that Heidegger sets himself the task of what he calls a "destruction" of the philosophical tradition. We shall see some of the implications of this in future entries, but the initial consequence is that Heidegger refuses to avail himself of the standard terminology of modern philosophy, with its talk of epistemology, subjectivity, representation, objective knowledge and the rest.

Heidegger has the audacity to go back to the drawing board and invent a new philosophical vocabulary. For example, he thinks that all conceptions of the human being as a subject, self, person, consciousness or indeed a mind-brain unity are hostages to a tradition of thinking whose presuppositions have not been thought through radically enough. Heidegger is nothing if not a radical thinker: a thinker who tries to dig down to the roots of our lived experience of the world rather than accepting the authority of tradition.

Heidegger's name for the human being is Dasein, a term which can be variously translated, but which is usually rendered as "being-there". The basic and very simple idea, as we will see in future entries, is that the human being is first and foremost not an isolated subject, cut off from a realm of objects that it wishes to know about. We are rather beings who are always already in the world, outside and alongside a world from which, for the most part, we do not distinguish ourselves.

What goes for Dasein also goes for many of Heidegger's other concepts. Sometimes this makes Being and Time a very tough read, which is not helped by the fact that Heidegger, more than any other modern philosopher, exploits the linguistic possibilities of his native language, in his case German. Although Macquarrie and Robinson, in their 1962 Blackwell English edition, produced one of the classics of modern philosophical translation, reading Being and Time can sometimes feel like wading through a conceptual mud of baroque and unfamiliar concepts.

The basic idea

That said, the basic idea of Being and Time is extremely simple: being is time. That is, what it means for a human being to be is to exist temporally in the stretch between birth and death. Being is time and time is finite, it comes to an end with our death. Therefore, if we want to understand what it means to be an authentic human being, then it is essential that we constantly project our lives onto the horizon of our death, what Heidegger calls "being-towards-death".

Crudely stated, for thinkers like St Paul, St Augustine, Luther and Kierkegaard, it is through the relation to God that the self finds itself. For Heidegger, the question of God's existence or non-existence has no philosophical relevance. The self can only become what it truly is through the confrontation with death, by making a meaning out of our finitude. If our being is finite, then what it means to be human consists in grasping this finitude, in "becoming who one is" in words of Nietzsche's that Heidegger liked to cite. We will show how this insight into finitude is deepened in later entries in relation to Heidegger's concepts of conscience and what he calls "ecstatic temporality".

Being and Time begins with a long, systematic introduction, followed by two divisions, each containing six chapters. I have just finished teaching the whole book in a 15-week lecture course at the New School for Social Research in New York and I estimate that I spoke for about 2 hours a week. As they say here in New York, just do the math! Therefore, in the following 7 short blog entries, I can only give a taste of the book and offer some signposts for readers who would like to explore further.

For a long time, Anglo-American philosophywas reproached for its detachment from life. It was said to be excessively concerned with the metaphysics of morals, that is the form and logic of moral judgments rather than their substance. I am not sure this was entirely justified, because, as Pascal reminds us, the two are not easily disentangled: "Let us labour, then, to think clearly, for such is the beginning of morality." But there is no doubt that these days philosophers concern themselves more than they once did with the hurly-burly of ordinary life.

Breakfast With Socratesis an attempt to illuminate daily life by means of philosophy and philosophy by means of daily life. I do not think it is at all successful. The first problem is style. The author, a British philosopher and management consultant, evidently feels it necessary sometimes to descend to demotic jocularity, no doubt for fear of losing his audience, and his vocabulary and tone are of the mid-Atlantic.

Then there is the structure. The first four chapters – "Waking up", "Getting ready", "Travelling to work", "Being at work" – lead us to suppose that the book will be a series of philosophical reflections on a normal day. But the next four chapters are "Going to the doctor", "Having lunch with your parents", "Bunking off" and "Shopping", as if the original organising principle were insufficiently strong to sustain a book and so arbitrary choice has been resorted to.

Then there are the errors, omissions and evasions. The book's first sentence does not inspire confidence: "Given that Socrates was assassinated by poison, you might think twice before accepting his invitation to breakfast." But is "assassination" the right word? Socrates took hemlock after being sentenced to death at his trial, refusing the opportunity to escape. Even if one accepts that this was assassination, Socrates did not know for most of his life that he was to be assassinated and neither would we. We would therefore have had no reason to turn down his invitation.

In a brief discussion of Hegel, Rowland Smith writes: "It would be far easier to mock Hegel's interpretation of history if it hadn't… provided grist to the Nazi mill." When he writes of Nietzsche, however, he fails to mention that he was the Nazis' favourite philosopher, perhaps because one of his own intellectual heroes, Foucault, was a Nietzschean; nor does he mention that Hegel was much more an intellectual progenitor of Marxism than of Nazism.

He writes approvingly of the true Nietzschean, happily shorn of supposedly bogus ethical idealism: "You'll be free to become yourself in all your nonconformist individuality – jagged, singular, wayward, defiant, eccentric, bold, unorthodox and original." I confess here that the figure of Dennis Nilsen, the serial killer who watched television with the corpses of his victims and disposed of them by flushing them down the drains, came to my mind. If anybody ever was jagged, bold, defiant and unorthodox...

A strong vein of intellectualised humbug runs through this book. For example, in "Going to the doctor", the author writes: "If love is a kind of illness, illness is a kind of love, on the grounds that it 'flies in the night', unpredictable and blind like the winged Cupid or a contagion you can't see coming…" Not to put too fine a point on it, this is drivel, by a man who sounds like he has very little experience, or even expectation, of real illness.

No thought is too banal for Rowland Smith; unfortunately, his banality is perfectly compatible with error. He rarely loses an opportunity to suppress what is true and suggest what is false. But the book has one redeeming feature: it proves how right Pascal was.

Theodore Dalrymple's latest book is Second Opinion (Monday Books)

Are the theory wars over? Twenty-five years ago you couldn't cocoa your cappuccino without someone accusing you of floating a signifier, much less close down the, ahem, discourse with a simple "I prefer my coffee that way". Who is this mythic "I", the theorists wanted to know, and how could he presume to know what he prefers? Has he forgotten he's as fictional as Oliver Twist or Mrs Dalloway? Doesn't he know that his likes and dislikes are as ideologically determined as the medium-term financial strategy?

College life these days looks rather less fraught. Theory is on the curriculum, to be sure. But the position you take on it no longer has any connection with your place in the world. Talk about the textual topography of the soul can be handy for seminars on Wuthering Heights, but even the most radically decentred subject must pay back their student loan. So theory won – because nowadays everyone "does" it. But theory lost – because nobody now does any more than "do" it. Like feigning Leavisian aliveness to the felt textures of the organic community, theory has become just another one of those things you affect to believe in in order to make a grade.

Which doesn't mean there was nothing to theory. As Gary Gutting reminds us in this dense but brisk account of the last half-century of what he calls philosophy's "French shenanigans", the likes of Jacques Derrida and Michel Foucault are the cream of the post-war continental intellects. In an age in which more than 40% of schoolchildren end up at "uni", students may like to ponder the fact that back in the 1950s, when the famous structuralists and deconstructionists-to-be were applying to read philosophy at Paris's École Normale Supérieure, a mere 35 people a year cut the metaphysical mustard. Indeed, as Gutting rather ungallantly points out, Foucault failed the entrance exam the first time around – and it took Derrida a full three attempts to get in.

What did they get from their studies? Chiefly, Gutting argues, an Oedipal urge to topple the Sartrean existentialism that had been all the rage since the war. And so, where Sartre talked of the individual's need to remake himself every day in the light of an indifferent or even hostile world, Foucault, Derrida and co professed to see only the indifference and hostility. The idea of man, of the individual consciousness struggling to get a hold on a world external to itself, was just that – an idea. And like all ideas it was a product of language, or, more precisely, language's ability to run rings around its putative users.

Because, so the theory goes, you don't speak language. Language speaks you. You might think of speech or writing as ways of expressing what's on your mind or in your heart but all you're really doing is mouthing the cliches that linguistic structures (and strictures) permit. Marx said man was alienated from his nature. Freud said man was alienated from his desires. But for the post-structuralists, the very idea of man was itself alienating. Had Descartes really had a self, he'd have been kidding it when he said, "I think, therefore I am". "I think, therefore I am being thought" is nearer to the deconstructionist mark. Or as Derrida more famously put it, "There is nothing outside the text".

But was there anything inside the texts of Derrida and his fellow deconstructionists? Gutting is scrupulously fair-minded on this point. On the one hand, he says (in an argument that gives him his title), post-structuralist thought has been no less than an attempt to "think the impossible".

On the other hand, impossible thinking makes for impossible writing, and he boldly admits that "for almost all of us (even those of us who spend a good amount of time on recent French philosophy), [it] cannot be understood through a close, line-by-line reading". Far better, he concludes, to treat this stuff like poetry – as essentially unparaphrasable and never fully explicable.

Fair enough, though I dare say I'm not the only one who finds Foucault and Derrida's coiling, arrhythmic stodge anything but poetic. Kant isn't much fun either, of course, but which of us would deny the certainty-subverting genius of the "first critique"? Rebarbatively obscurantist the post-structuralists may be, but anyone who has read Gary Gutting's fine introduction to their thought will be a little less quick to convict them of charlatanry.

Christopher Bray is working on a history of 1960s culture and politics