For the problem with Voltaire and Berlin is not that they are absurd or lack serious purpose -- it is hard to think of a more serious purpose than their rebukes of fatalism -- it is that they fail to take into account the limits or constraints with which elected officials must deal. Constraints are, by definition, fatalistic because they draw on physical facts or a long history of experience that illuminates relatively fixed patterns: patterns that simply cannot be ignored. It is easy to say, let's intervene and establish a humanistic democracy in this place, but if you do so against geographical and political constraints, and against much advice to the contrary, you are being very foolish, even if you are opposing fate.
To refuse all constraints and limits is frankly illogical. And Voltaire and Berlin intuited this. They were reproaching a tendency to be too fatalistic: They were speaking up in favor of the moral responsibility to struggle in order to improve the world. They were, after all, not engaging in absolutes.
Enter geopolitics, or at least a healthy version of it. Healthy geopolitics accepts moral struggles. It accepts the actions of policymakers to better the situation of their own people and people elsewhere on the planet. Healthy geopolitics comprehends that national leaders will periodically act in an idealistic manner, because without such idealism a nation like the United States -- founded on principles as well as on interests -- can be in danger of losing its very identity. Thus, geopolitics does not deny that the appeals for human agency on the editorial pages have value. Geopolitics does not deny human agency. But it does posit that there is another half of the story: the half that it is all about constraints, loosely defined as fatalistic.
Indeed, the humanist will say that the Taiwanese people enjoy de facto independence from mainland China because of the age-old, historic struggle for freedom and human dignity. The geopolitician will acknowledge this, while also pointing out that the Taiwanese are independent primarily because their island of Formosa is roughly 160 kilometers (100 miles) from the Chinese mainland: had it been about 30 kilometers -- the width of the English Channel -- Mao Zedong's forces would likely have conquered it more than 60 years ago. The humanist will say the United States fought fascist Japan and Nazi Germany to preserve human freedom; the geopolitician will say World War II was fought to preserve the balance of power in the Eastern Hemisphere, which Japan and Germany threatened to overturn.
The humanist interpretation of history is more aesthetic, more appealing and therefore more beautiful; the geopolitician's interpretation is more mechanical, more practical and therefore lowering and less appealing. But that does not make it any less accurate, or less urgent for the policymaker to bear in mind. The policymaker will always voice publicly the sentiments of Voltaire and Berlin, while privately listening to the counsel of geopoliticians like Halford Mackinder and Henry Kissinger.
In truth, the policymaker is forced to be a partial fatalist. He is aware that some battles have to be fought against great odds and against the forces of determinism. But he is also aware that much has to be conceded as just too powerful to overcome: or else, a foreign policy would be unsustainable, because of all the humanitarian causes and intervention scenarios that would no doubt arise.