So far we have considered ordinary doubts that people may suffer from in the course of their everyday existence. However, we now come to the thorny question of to what extent it is possible for there to be such a thing as "global" scepticism - that is, doubt about everything which we experience.

To illustrate this it is necessary to distinguish between ordinary doubt and what is called "philosophical doubt". We all experience ordinary doubt: "Did I leave the iron on?", "Is Jim in a mood with me?", etc. These doubts are doubts about facts. If I go back home, I can check if the iron is still on; if I talk to Jim, I may find out if I have done something to offend him.

Philosophical doubts are different. In the above situations, examples of philosophical doubts would be: is it possible to really tell if the iron is on; can I really find out if Jim is angry with me - or even more radically, if Jim is actually there (and not some figment of my imagination - or a robot!).

Before moving on, have a think about this difference and try to get it clear in your head. Ordinary doubt - or local scepticism - can usually be tested - and even when it can't, there may well come a time when it can. So, I may currently have doubts about whether there is life on some distant planet; however, in the future, technology may eventually allow me to actually find out (the development of a more powerful telescope, for instance).

However, philosophical doubt - or global scepticism - seems to deny the possibility of there being any conclusive way of finding out. For instance, if in regard to the question of life on some other planet someone argued, "We can never really know that there is not life on another planet because it may be undetectable to us," then that person is a sceptic.

This sort of doubt is largely responsible for the reputation which philosophy seems to have in some quarters of being absurd and unrealistic. "Do you think that table is really there?" the philosopher asks. "You think you are talking to me, but what proof do you have?" However, the underlying point is a serious one: how can we ever really know something with absolute certainty? Remember, no matter how certain we are, there is always room for doubt. Even something like science, which uses experiment to prove theories, sometimes finds new truths which seem to contradict old ones (Einstein's theory of Relativity, for example).

In summary, scepticism attacks certain beliefs that most of us hold to be true:

• It is sometimes possible to be certain about something.
• Our senses are mostly trustworthy.
• We can eventually find out whether we have been mistaken or not.
• It is possible to experience reality as it really is.

Exercise: Before moving on to the next section, I want you to do two things. Firstly, make a list of what you think are sceptical arguments (you can base them on the examples I have already given, but try to think of your own - 3 or 4 should do). Secondly, try to identify answers that you think a non-sceptic could use to show that these problems do not exist. Is it possible to do it?

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