This text is a revised and augmented version of a speech delivered in Rome on February 21, 2020, on the occasion of the inaugural assembly of the «Towards a Constitution of the Earth» movement. The speech begins by stating the global problems on whose solution the survival of humanity depends: climate change and its consequences; the renewed nuclear danger; the growth of inequalities; the abnormal dimensions of poverty, of deaths from hunger and lack of care, of the migrations of desperate people who try to escape these evils. To face these problems, it is pointed out that a supranational constitutionalism is necessary, capable of establishing principles and rules with universal validity to protect the fundamental rights of all the inhabitants of the planet, and to create global guarantee institutions that make them effective, such as a health service world, a world organization of work and education, a planetary public property, a global tax system. This «Constitution of the Earth» is presented as an expansion of the constitutional paradigm beyond the State, in three directions: towards a constitutionalism of international as well as national law, of private as well as public law, of fundamental goods as well as of fundamental rights. Only in this enlarged dimension would constitutionalism be able to face the environmental emergency, prevent new ecological catastrophes;
the emergence of wars, terrorism and major crime, effectively banning weapons of all kinds; the social emergency, providing the means to heal inequalities, poverty, hunger and disease. In the Post scriptum, written in May 2020, the author indicates the immediate lessons that should be drawn from the COVID-19 pandemic: the irreplaceable value of public health, and the need for a strengthening and radical reform of the WHO and other possible world public institutions which should be responsible for a global governance of global danger.