Glossary: Look out, he's a bit of a personality

KELVIN MacKENZIE's explanation that he was leaving BSkyB because of a 'personality clash' moved only seven-eighths of the way towards absolute candour.

It's true that he didn't mess about with 'spending more time with his family' (he has recently gone back to his wife after a separation) or with a wish 'to broaden his horizons 1 ' but 'personality clash' is still a euphemism, actually a more decorous way of saying 'I hate my boss's guts'. To note of someone, with a rueful smile, that 'he's a bit of a personality' is to send fair warning to most people that it may be time to cross the street.

MacKenzie was also engaging in a last flourish of territorial combat. To have a personality is pretty mundane - even the drabbest of us can manage that - but to be a personality is something quite different. MacKenzie may have lost the 'this company ain't big enough for both of us' showdown, but he could still assert his own scale as he rode out of town, even hint that it may have been the winner who could not deal with the competition. The front-page coverage that has been given to his resignation rather proves his point.

As it happens, a 'personality clash' is a peculiarly 20th-century notion, even if it has its roots in older usage. Personality first meant simply the condition of being a person rather than a thing. To debate the personality of God was not to wonder whether he was crabby at breakfast but to raise the theological matter of his existence as an identifiable Being.

From the late 18th century, 'personality' is also used to mean the particular group of qualities that distinguish a person from all others. In fact, under this sense you don't even have to be a person to have a personality. Kelvin MacKenzie, for instance, gave the Sun a distinctive personality - boorish 2 , thuggishly witty, given to lachrymose tendencies where 'kiddies' and 'mums' were concerned. But personality remains indivisible, a fingerprint marking one person's separateness from another.

In this century the word has been appropriated by psychology and sociology to a subtly different end. Personality becomes a way of describing the object of study, a way of reducing the infinite variety of human character to a set of categories which can be measured and assessed with some exactitude. Spurious exactitude in many cases, but often plausible enough to escape unnoticed. It becomes possible to 'diagnose personality' and to conduct 'personality inventories', as if human nature consisted of a set of basic parts, variously selected and assembled.

In the Thirties and Forties, psychologists were prone to discuss anti-social behaviour in terms of 'personality defects', as if the problem was susceptible to the replacement of a dodgy component or a bit of quick mental spanner 3 work. 'His personality' isn't necessarily his alone any more - it might be shared with any number of others, as concepts such as 'the authoritarian personality' suggest.

Towards the end of the 19th century you could also, for the first time, be 'a personality'. The Oxford English Dictionary's first citation is from George Bernard Shaw in 1889, in which he defines the phrase as 'a man pre-eminently himself, impossible to disguise'. This notion of distinctiveness (at odds with the psychologist's boxes of types) is why it applies only to certain types of celebrity - we talk of film stars rather than film personalities because the notion of disguise is central to acting. However thuddingly interchangeable Arnold Schwarzenegger's different roles are, a vestigial idea of dissembling attaches to his appearances.

A television personality, too, is far more likely to be someone who notionally appears in his own character than, say, a soap actor. The highest praise for a Sue Lawley or a Jonathan Ross is to say 'they're just themselves', whatever degree of artifice is required to sustain the illusion.

There is an odd twist here, because the origins of the word are precisely the opposite. The word 'person' derives from the Latin persona, a mask as used by actors (possibly from personare, to sound through). So a person was an actor, a public entity, defined by his or her social interactions with other actors, not by some concealed essence of individuality. In this sense, the psychologists, with their set of dramatic types acting out particular roles, hark back to a far more ancient notion of human behaviour.

Kelvin MacKenzie's 'personality clash' belongs to the more mechanistic view of human behaviour. Just as people say 'the chemistry was just wrong', it suggests that immutable laws are involved in activities which, in fact, are perfectly susceptible to human adjustment. That sort of behaviour, though, is one of the ways by which you recognise a real personality.

1 From the Greek horizein, bound or limit.

2 From the Old English ebur, meaning dweller, farmer, countryman. Formed from bur, which meant dwelling, house, cottage. Cf neighbour - near or 'nigh' dweller.

3 From the Flemish, Low German spannen (Old English spannan), to fix, fasten or join.