But not even here does evolution take place without revolutions. What is true of a man's views, of the climate of a country, of the characteristics of a species, is true also of societies: "they evolve slowly, but there are also times of the quickest transformation."[452] For circumstances of many kinds may oppose themselves to the effort of human associations to attain to the greatest possible measure of happiness.[453] "New thoughts germinate everywhere, try to get to the light, try to get themselves applied in life; but they are kept back by the inertia of those who have an interest in keeping up the old conditions, they are stifled under long-established prejudices and traditions."[454] "Political, economic, and social institutions fall in ruins, and the building which has become uninhabitable hinders the development of what is sprouting in its crevices and around it."[455] Then there is need of "great events which rudely break the thread of history and hurl mankind out of its ruts into new roads";[456] "the Revolution becomes a peremptory necessity."[457]--"Man has recognized his place in nature; he has recognized that his institutions are his work and can be refashioned by him alone."[458] "What has not the engineer's art dared, and what do not literature, painting, music, the drama dare to-day?"[459] Thus must we also, where any institutions hinder the progress of society, "dare the fight, to make a rich and overflowing life possible to all."[460] 2. From the evolutionary law of the progress of mankind from a less happy existence to the happiest existence possible Kropotkin derives the commandment of justice and the commandment of energy. In the struggle for existence human societies evolve toward a condition in which there are given the best conditions for the attainment of the greatest happiness of mankind.[461] When we describe anything as "good," we mean by this that it favors the attainment of the goal; that is, it is beneficial to the society in which we live; and we call that "evil" which in our opinion hinders the attainment of the goal, that is, is harmful to the society we live in.[462] Now, men's views as to what favors and what hinders the establishment of the best conditions for the attainment of mankind's greatest happiness, and hence as to what is beneficial or harmful to society, may certainly change.[463] But one fundamental requisite for the attainment of the goal will always have to be recognized as such, whatever the diversity of opinions. It "may be summed up in the sentence 'Do to others as you would have it done to you in the like case'."[464] But this sentence "is nothing else than the principle of equality";[465] and equality, in turn, "means the same as equity,"[466] "solidarity,"[467] "justice."[468]