Extreme views in the debate about any form of cannabis decriminalisation are advanced with almost religious fervour.
On the one hand, some assert that cannabis is a dangerous, highly addictive drug which causes schizophrenia, and that any move to relax prohibition would be a disaster.
On the other hand, there are those who have used cannabis for years, swearing it causes no trouble.
On Tuesday the debate will once again take off, following the publication of an All-Party Parliamentary Group (APPG) report recommending the legalisation of pharmaceutically produced cannabis for medical use only.
And listen carefully to the evidence.
The MPs will set out an argument for enabling doctors to prescribe cannabis which has been produced in a strictly controlled pharmaceutical setting, and recommend facilitating further research on its therapeutic properties.
They will recommend it is made available to treat around 60 specific conditions.
And they will look at the global context.
Access to cannabis as a medicine is now allowed in Canada, the Netherlands, Australia, Israel, and over 20 states in the US. Germany and Switzerland allow it to be imported from the Netherlands for medicinal purposes.
Medical opinion is changing.
In Europe more than 250 million people now have legal access to medicinal cannabis, 210 million in the USA, 35 million in Canada and 8 million in Israel.
'Penny' is one of those who uses cannabis as medicine.
A British woman, she moved to Holland so that she could access the drug legally there to help her deal with complex medical conditions which include Multiple Sclerosis. If the law was changed in the UK she would come home.
She says she left everything – "home, family, job, and friends" - in order to have access to medical cannabis.
Jacob still lives in the UK and also supports a change in the law. He has being taking cannabis in small doses for seven years for chronic pain due to serious ill health.
He hates breaking the law but says he has no choice because he needs cannabis as a pain relief to make his life bearable.
Baroness Molly Meacher, who chaired the APPG committee recommending the changes to the law is emphatic.
She says 30,000 people now access the drug illegally for medical reasons – putting themselves at risk, paying criminal dealers and fueling a black market in drugs.
She says that more than one million people could benefit from making the drug available as a controlled medicine “saving the NHS millions”
She also states that public opinion is now in favour of a change.
But there is still considerable opposition to any change in the law.
The British Medical Association remains firmly opposed.
They have concerns about any pharmaceutical drug finding its way onto the recreational market and also about the possible psychotic and addictive side effects. Those advocating a change in the law maintain that there would be less risk of either with specially produced and controlled cannabis.
Tuesday's support will certainly fuel the debate, and may even be a "tipping point" policy moment, but no change is likely for a long time yet.