egeneration of the psyche, its redirection from lower to higher levels,
can never be accomplished without their help. We only rise to the top of
our powers when the whole man acts together, urged by an enthusiasm or
an instinctive need.

Further, a complete and ungraduated response to stimulus--an
"all-or-none reaction"--is characteristic of the instinctive life and of
the instinctive life alone. Those whom it rules for the time give
themselves wholly to it; and so display a power far beyond that of the
critical and the controlled. Thus, fear or rage will often confer
abnormal strength and agility. A really dominant instinct is a veritable
source of psycho-physical energy, unifying and maintaining in vigour all
the activities directed to its fulfilment.[74] A young man in love is
stimulated not only to emotional ardour, but also to hard work in the
interests of the future home. The explorer develops amazing powers of
endurance; the inventor in the ecstasy of creation draws on deep vital
forces, and may carry on for long periods without sleep or food. If we
apply this law to the great examples of the spiritual life, we see in
the vigour and totality of their self-giving to spiritual interests a
mark of instinctive action; and in the power, the indifference to
hardship which these selves develop, the result of unification, of an
"all-or-none" response to the religious or philanthropic stimulus. It
helps us to understand the cheerful austerities of the true ascetic; the
superhuman achievement of St. Paul, little hindered by the "thorn in the
flesh"; the career of St. Joan of Arc; the way in which St. Teresa or
St. Ignatius, tormented by ill-health, yet brought their great
conceptions to birth; the powers of resistance displayed by George Fox
and other Quaker saints. It explains Mary Slessor living and working
bare-foot and bare-headed under the tropical sun, disdaining the use of
mosquito nets, eating native food, and taking with impunity daily risks
fatal to the average European.[75] It shows us, too, why the great
heroes of the spiritual life so seldom think out their positions, or
husband their powers. They act because they are impelled: often in
defiance of all prudent considerations! yet commonly with an amazing
success. Thus General Booth has said that he was driven by "the impulses
and urgings of an undying ambition" to save souls. What was this impulse
and urge? It was the instinctive energy of a great nature in a