The great increase in world population in the coming century will resu
lt in a human crisis of worldwide proportions. A new concept for descr
ibing and proposing solutions to this crisis, called the Trilemma, is
described by the authors. To feed large and growing populations, human
kind is now being forced to make the difficult choice between producin
g sufficient food for the world population and preserving the environm
ent, or generating economic growth, requiring the consumption of energ
y and natural resources. These difficult choices present the Trilemma,
a new concept that is composed of three dimensions: economic growth,
resources such as energy and food, and the environment. None of these
three dimensions can be optimized individually as they are mutually in
terdependent. This paper describes a possible world energy condition i
n the 21st century. Three scenarios of this energy consumption are pre
sented and compared with the possible energy supply at that time. This
supply is estimated from the extrapolation of the renewable energy de
velopment of the past and the possible fossil fuel supply. The compari
son of the energy supply and the energy consumption indicates that the
annual rate of economic growth in the developed region would be only
1% if the gross national product (GNP) per capita of the developing re
gion increases gradually from 1/26 of the GNP of the developed regions
in 1990, to 1/10 in 2020, and finally to 1/3 in 2100. Another possibi
lity is that if the GNP per capita of the developing region remains 1/
26 of the GNP of the developed regions between 1990 and 2100, the econ
omic growth rate in the developed region could be as large as 3%. In t
he latter case, an energy shortage would develop in the middle of the
21st century, even if the fast breeder reactor were fully operational
by the year 2030. Energy technological developments in Japan are also
described as a part of the possible countermeasures against the Trilem
ma.