Which of these is definitely true? Elvis Presley is alive and living in Acapulco. Genetically modified foods are safe. Mobile phone masts are dangerous. Taking vitamin supplements makes you healthy. Genetically modified foods are dangerous. Horoscopes can tell you the future. Organic foods are better for you than non-organic. Natural radiation is safer than radiation from nuclear power plants. Answer: none of them.
None of these statements can be proven true, although it is remarkable how many people firmly believe these things, even the notion that Elvis might be working on his tan in Mexico. Some can get positively vehement about these issues, despite having very little real evidence to prove their view.
Take the mobile phone mast issue, for example. Violent protests have erupted in several parts of the State as locals campaigned to keep these masts out of their neighbourhoods. The standard claim is that they pose "a genuine risk to health", but in fact you are more likely to be harmed by a mast falling over than from the signal it sends out.
The real reason people don't want the masts is that they are ugly, but it is simpler to claim and to believe that they are a health risk. It is also easier to rally opposition if you can scare people into believing they are in danger.
It is much more difficult to convince people that there is emerging evidence that the mobile phones themselves, and not the masts, may pose a risk. Only this month researchers at Bristol Royal Infirmary released a study which showed that subjects exposed to radiation from mobiles experienced temporary disruption of memory.
People want their mobiles, however, and so ignore these findings. The masts are out because they are a danger but the phones are OK because we want them.
This confusion, which unfortunately cannot be resolved by applying simple scientific facts, all boils down to the way we deal with the risks - natural and human-made - that follow us around like shadows on a sunny day. We disregard any dangers associated with the things we want and run scared before those we view as optional.
All the medical studies which show that cigarette-smokers die young don't amount to a pile of ash to those addicted to nicotine, who will continue to smoke and risk their lives. We don't think or worry about invisible, radioactive Radon gas in our homes but lose sleep over Sellafield, even though Radon poses the greater day-today risk.
We happily gobble up greasy fries, heavily processed foods with high salt and fat content, bags of crisps and other nasties that gum up our blood vessels and are proven to be dangerous.
Many consumers, however, are up in arms about foods, such as soya and maize, that contain genetically modified ingredients despite a growing body of evidence that modified foods aren't any different when digested than their unmodified equivalents.
This is not to argue in favour of genetic modification, Sellafield or any other potential source of risk. It is a matter of recognising that all foods, lifestyles and activities carry a potential for risk, but also that we do not tend to apply logic or reason when deciding if we find a risk tolerable.
Train crashes are rare but do happen and so every journey carries a risk even though we treat this reality with indifference. Drinking too much is bad but statistics can show that drinking a little is better than not drinking at all if you want a long life.
Vaccinating children against measles involves a measurable risk of serious health damage, but statistically it is more dangerous for the child not to be vaccinated.
The level of risk doesn't change very much, but our view of the relative "riskiness" of a food or activity does. Hands up those who recall the scare stories when microwave ovens were first introduced. We were told - backed up by alleged evidence - that carcinogens would be produced by the microwaves. Few homes are without microwaves nowadays.
E numbers, the food additives put into processed foods for flavouring, colouring and thickening, were also a major issue. A whole range of ills was blamed on these additives, and there is no doubt some individuals allergic to certain products did suffer from their consumption.
Concern about these has passed, however, to be replaced by worries about GM foods. The great majority of studies done so far on GM foods haven't shown these are dangerous, but perhaps the risks are well hidden and difficult to find, or so those opposed to the technology argue.
There are also potential environmental risks, for example, the spread of modified genes into the wild to unknown effect or the loss of bio-diversity if farmers go for modified crops.
Research is ongoing into what some have dubbed "Frankenstein foods", so a cautious commentator should check where the balance of scientific evidence lies. At the moment this suggests that there is little risk from eating modified products, although the jury is out about the environmental issues.
Why then is there such a furore at the moment about GM foods and what has governments across Europe running scared before an electorate that is not convinced about safety aspects? This is where perception of risk comes into play again and evidence goes out the window.
Opponents of the technology keep banging away at the possible health risks of these products, even though no definitive evidence has yet been shown. The consumer doesn't know for sure but does not see any advantage in accepting any extra risk, real or otherwise.
These products make money for their manufacturers and for food producers but are of no direct benefit to us so far. So we reject these optional risks just in case. The same process occurs wherever a community rejects a phone mast or, as happened in Cork, proposals for overland electricity pylons.
It would have been better had Cork councillors changed their minds about the pylons for the real reason - because they are a blot on the landscape and because they are frightened of the anger of the electorate - rather than on the spurious health claims made by opponents who once again cited scientific certainties about power lines, when none exists.