The one central idea throughout all the Upanishads is that of realisation. A great many questions will arise from time to time, and especially to the modern man. There will be the question of utility, there will be various other questions, but in all we shall find that we are prompted by our past associations. It is association of ideas that has such a tremendous power over our minds. To those who from childhood have always heard of a Personal God and the personality of the mind, these ideas will of course appear very stern and harsh, but if they listen to them and think over them, they will become part of their lives and will no longer frighten them. The great question that generally arises is the utility of philosophy. To that there can be only one answer: if on the utilitarian ground it is good for men to seek for pleasure, why should not those whose pleasure is in religious speculation seek for that? Because sense-enjoyments please many, they seek for them, but there may be others whom they do not please, who want higher enjoyment. The dog's pleasure is only in eating and drinking. The dog cannot understand the pleasure of the scientist who gives up everything, and, perhaps, dwells on the top of a mountain to observe the position of certain stars. The dogs may smile at him and think he is a madman.