(Carl Sagan, "As variedades da experiência científica, Uma visão pessoal da procura de Deus", Gradiva, 2007, pp. 199-201)
Dotado de uma notável inteligência, Carl Sagan será, para muitos, um autor a ser lido e respeitado sob condição - é que ele não é crente de nenhum deus; e nem os mais sinceros, piedosos e tolerantes crentes em deuses, especialmente os crentes monoteístas, em última instância, aceitarão o que ele afirme, ou sequer hipotetize - em última instância, nos temas em que a ciência confronte a crença, a força da crença faz tombar o peso da balança, sempre para o mesmo lado. A tolerância de um crente está sempre dependente de a essência do seu deus, qualquer que ele seja, não ser posta em causa - e isto é uma forma de intolerância; de radical intolerância.
Noutra conferência, da série donde fui buscar as afirmações que destaquei, Sagan diz:
«Num universo complexo, numa sociedade que passa por mudanças inéditas, como poderemos encontrar a verdade se não estamos dispostos a questionar tudo e a dar uma oportunidade igual a tudo? Há uma tacanhez de mente a nível mundial que põe em perigo a espécie.» (mesma obra, pág. 223)
«[...] Consider our past circumstances. Imagine our ancestors, a small, itinerant, nomadic group of hunter-gatherer people. Surely there was change in their lives. The last ice age must have been quite a challenge some ten to twenty thousand years ago. There must have been droughts and new animals suddenly migrating into their area. Of course there is change. But by and large the change is extraordinarily slow. The same traditions for chipping stone to make spears and arrowheads, for example, continues in the East African paleoanthropological sites for tens or hundreds of thousands of years.
In such a society, the external change was slow compared to the human generation time. Back then traditional wisdom, parental prescriptions, were perfectly valid and appropriate for generations. Children growing up of course paid the closest attention to these traditions, because they represented a kind of elixir of the wisdom of previous generations; it was constantly tested, and it constantly worked. It is not for nothing that ancestors were venerated. They were heroes to subsequent generations, because they passed on wisdom that could preserve lives and save them.
Now compare that with another reality, one in which the external changes, social or biological or climatic or whatever we wish, are rapid compared to a human generation time. Then parental wisdom may not be relevant to present circumstances. Then what we ourselves were taught and learned as youngsters may have dubious relevance to the circumstances of the day. Then there is a kind of intergenerational conflict, and that conflict is not restricted to intergenerational but is also intragenerational, internally, because the part of us that was trained twenty years ago, let's say, must be in some conflict with the part of us that is trying to deal with the difficulties of today. So I claim that there are very different ways of thinking for these two circumstances: when change is slow compared to a generation time and when change is fast compared to a generation time. There are different survival strategies. And I would also like to suggest that there has never been a moment in the history of the human species in which so much change has happened as in our time. In fact, it can be argued that in many respects there never will be a time when the change can be so rapid as it has been in our generation.
For example, consider transportation and communication. Just a couple of centuries ago, the fastest practicable means of transportation was horseback. Well, now it is essentially the intercontinental ballistic missile. That is an improvement from tens of miles per hour to tens of miles per second in velocity. It's a very substantial increment. In communication a few centuries ago, except for rarely used semaphore and smoke-signaling systems, the speed of communication was again the speed of the horse. Today the speed of communication is the speed of light, faster than which nothing can go. And that represents a change from tens of miles per hour to 186,000 miles per second. And never will there be any improvement on that velocity.
Now, it's a very different world if the fastest that a message can get to us goes from the speed of a horse or a caravel to the speed of light. The speed of light means that we can talk—in essentially real time—to anybody on the Earth or even on the Moon. [...]» (Sagan, Carl. The varieties of scientific experience. A Personal View of the Search for God. The Penguin Press. New York. 2006)And...
«In a complex universe, in a society undergoing unprecedented change, how can we find the truth if we are not willing to question everything and to give a fair hearing to everything? There is a worldwide closedmindedness that imperils the species.»