The definition of the word ‘navigation’ has been discussed frequently in meetings of this Institute and a very flexible thing it appears to be, varying its scope to suit the lecturer. This is not really surprising however, since whatever we think of as ‘navigation’ is only part of the wider business of living. In aviation for instance, the business of ‘conducting a craft as it moves about its ways’ can legitimately include seeing that the fuel tanks are full as well as pulling back on the stick to avoid hitting the top of the hill.