The most convincing proof that the increase of violent crimes in spring has no direct connection with the heat, is found in the fact that this increase is already very great in the months in which in the North of Europe there is absolutely no question of heat properly so called (i.e. in March and April); and in the second place the course of crimes during the week must be noted, with the maximum on Sunday, when naturally the heat is no greater than on other days; and in the third place, the maximum is not to be found at the hottest time of the day. [122] The increase of sexual crimes in hot seasons is in part only apparent, because those who commit these crimes then operate more out of doors, and a greater number of arrests results. For the rest, it must be conceded that the sexual instinct in general is quickened a little during the spring and summer, and as a consequence sexual acts increase. But this does not mean that these acts are therefore criminal. The principal reason why sexual crimes increase during the hot weather is to be found in opportunity, which occurs much more frequently than in cold weather. The proverb says: “opportunity makes the thief”, and this is still more applicable to sexual criminals. [123] I am therefore of the opinion that the social factors must not be included in the etiology of crime. They have their influence upon the structure of society, they have also their influence upon man, but it depends upon social conditions whether this influence takes a criminal direction or not. [124] Before taking up our analysis of “Socialismo e criminalità”, I would remark that this division of the factors into three groups has to do exclusively with the individual criminal, and thus loses sight of the question why such an action in any place whatever, at any time whatever, is regarded as criminal? Such a query brings out the fact that we are here concerned with social factors only.