It is the desire for explanations that are at once systematic and controllable by factual evidence that generates science; and it is the organization and classification of knowledge on the basis of explanatory principles that is the distinctive goal of the sciences.
Interpretation
The quote emphasizes that science is driven by a quest for systematic explanations backed by factual evidence.
Ernest Nagel argues that the fundamental essence of science lies in the desire to understand the world through systematic and empirical explanations. This pursuit not only requires evidence but also aims at organizing and classifying knowledge according to clear explanatory principles, underscoring the structured approach that characterizes scientific inquiry.
In practice
In a lecture about the importance of science, one might quote this to emphasize the value of systematic inquiry.
It {Darwin's theory of evolution] was a concept of such stunning simplicity, but it gave rise, naturally, to all of the infinite and baffling complexity of life. The awe it inspired in me made the awe that people talk about in respect of religious experience seem, frankly, silly beside it. I'd take the awe of understanding over the awe of ignorance any day.
Our senses enable us to perceive only a minute portion of the outside world.
Mathematics brought rigor to Economics. Unfortunately, it also brought mortis.
There is no scientific reason to think that we, even with space travel, are going to survive as a species for ever, certainly not by biting off the hand that feeds us, which is exactly what we are doing.
There is much that science doesn't understand, many mysteries still to be resolved. In a Universe tens of billions of light-years across and some ten or fifteen billion years old, this may be the case forever. We are constantly stumbling on new surprises
It will free man from the remaining chains, the chains of gravity which still tie him to this planet.
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