One of the most common objections leveled against scepticism is that however consistent it is in itself, it cannot be serious. Sceptical doubts are not real doubts but only theoretical. Furthermore, it would be impossible to put sceptical theory into practice, for to be consistently sceptical, so it is held, would be to sentence oneself to a life of inactivity; as soon as one begins to do something, one begins to take certain things for granted, to believe in them and hence not to doubt them.