 Not acting till you have a good idea of any adverse consequences is called the precautionary principle. This happens every day. Products are tested before they go to market to prove that they're safe, because there's a chance that they're not. But it's difficult to remove all concerns about the risks associated with every single action, let alone those based on the complex series of tests and observations required by science. And here we run into some confusion about how science works. Some say global warming and evolution aren't facts, they're just theories. But there's no just about it. In science the word theory doesn't mean I reckon, it means a well tested rule which is based on logic, explains repeated observations and has been used to make accurate predictions. This makes them incredibly useful and difficult to ignore. Newton's theory of gravitational attraction is a theory. It explains how objects with mass move the way they do. It's a theory so useful that some 300 years after it was first published it's still used to send objects from Earth to the far reaches of the solar system. Observable or proven facts are only part of science. When we're faced with risks it's natural to want to wait till there's 100% certainty about it. Unfortunately that's impossible. The best that can be achieved is that given all our current theories, repeated testing, logic and the facts that we're reasonably confident something is safe. And this is where the precautionary principle can be misused. Waiting for more information is useful but waiting for that unattainable 100% certainty prevents anybody from doing anything. Consider mobile phones and fears that their radiation emissions may cause cancer. If we choose to wait until mobile phones were proven to be 100% safe or not we would have no mobile phone technology. Cancer is not something to be taken lightly and concerns should never be dismissed but waiting for irrefutable data which is logically impossible is a bad way to make decisions. And by doing so we may lose amazing opportunities or encounter new risks. Thinking about risks is sensible but demanding 100% safety stops technology from evolving.