"We won't be able to understand the brain. It is the most complex thing in the universe," says Professor Sir Robin Murray, one of the UK's leading psychiatrists.
However, during his 40-year career the professor has made great strides in his attempt to find out why brains go wrong, especially in schizophrenia - a condition he thinks is often misunderstood and "demonized" in the media.
"Schizophrenia is just a posh name for people who have hallucinations," Professor Sir Robin Murray told BBC Scotland's Stark Talk programme .
"They hear voices or they have delusions. They have bizarre ideas which are not supported by the facts and they stick to these beliefs," he says.
Often these beliefs are "paranoid" - a feeling that people are against them - or they may be "grandiose", thinking they are on a special mission, he says.
"If you are hearing things or have strange beliefs you tend to behave in a bizarre manner as well sometimes," Prof Murray says.
The 68-year-old, who was born in rural Berwickshire and went to school in Edinburgh, was not always so comfortable and understanding around mental illness.
While studying medicine at Glasgow University, he took free lodging at Leverndale, which was then referred to as a mental hospital.
He says: "When I went to Leverndale I was very worried.
"My bedroom door did not have a lock on it so I moved a table and a chair and wedged them against the door in case some mad men came in with an axe.
"It took me a few days before I realised this was a daft thing to do."
Over his time there he got to know the patients and became "fascinated" by them.
"The amazing thing about schizophrenia is these are people who have to live their life without being able to believe their senses. When you or I hear something we know that it is real."
In the early 1970s he went to London and the Maudsley hospital, a specialist psychosis unit.
He says that there were ideological wars going on at the time about the causes of schizophrenia.
Some thought it was a biological illness, while others believed it was a social condition. Neither side had the evidence to back up their claims.
Prof Murray has spent many years researching and studying the evidence.
Over the years he has showed that environmental factors, difficulties at birth, social problems and drug abuse could all eventually result in schizophrenia.
In the past decade Prof Murray has been involved in the debate over whether heavy use of cannabis could contribute to the onset of psychosis.
In 2004, he wrote a book called Marijuana and madness and has published several papers on the subject.
Prof Murray warns about the modern, stronger versions of cannabis, known as Skunk.
He says it is now easier to convince people of the link between heavy use and psychosis because many have seen the evidence for themselves.
Prof Murray says: "When they get into their 20s they know someone who at school was smart and doing very well and 10 years later they seem to have lost some of their abilities or maybe they have gone psychotic.
"This is a minority of people. The vast majority of people who have taken cannabis are fine with it.
"However, if they are smoking five or six joints a day you ought to be pretty wary and pretty worried.
"Certainly when we look at people coming into our hospital they are very much more likely to be taking skunk every day than the general population."
Prof Murray also warns that drugs such as amphetamine and cocaine can cause psychosis because they increase a chemical in the brain called dopamine. He says all the drugs used to treat schizophrenia block dopamine.
An earlier study compared the incidence of the condition in inner city London with the rate in rural Dumfriesshire and he found schizophrenia is a "disorder of the inner city", particularly poor areas.
There is also an increased risk of the condition among migrants which Prof Murray puts down to feelings of alienation and dislocation.
"Being in a foreign country or a country where you don't quite understand the customs and you may misunderstand things makes you more prone to paranoia," he says.
Prof Murray says that, as a Scot, he "identifies with the underdog".
"One of the reasons I stay working where I am is because I like working with the poor and the disadvantaged. So working in Camberwell is very good because there are lots of disadvantaged people.
"Schizophrenia occurs in the disadvantaged and the alienated. It is good to see if one can do a little to reverse some of the difficulties such people have."