It is no exaggeration to say that research into modern history in Japan was born out of reflection on the war. Now that Japan has become a "pacifist" nation, which is one of the basic principles of the Japanese Constitution, we are considering applying the lessons learned from research into modern history to global security issues. In Japan, peace and military power are perceived as contradictory, but globally, peace and military power are two sides of the same coin.

Possessing sufficient military power runs the risk of increasing fear on both sides and inciting war, but it can also cause the other side to hesitate about bringing the country into a state of war. This means that conversely, "pacifism" can also provoke military action from other countries. On the other hand, in modern times, countries around the world have mutual interests in a variety of areas, from economy to culture, which creates a situation in which economic reciprocity exists and both sides would suffer great damage if they were to go to war. Security theory is extremely complex.

The idea of security is based on the prospect theory, which says that people place more importance on losses than on gains. Prospect theory is a representative result of behavioral economics based on psychology. For example, if you drop your wallet with 10,000 yen in it, you will desperately search for it, but if someone tells you that your wallet with 10,000 yen in it is somewhere, you won't search for it very hard. The reference point is an important factor in this judgment. When searching for your wallet, the reference point is "before you lost your wallet." On the other hand, when you don't search for your wallet, the reference point is "now, when you don't have your wallet," so no loss occurs.

If we think about this in terms of war, for example, just before the Pacific War, Japan was in the midst of the Second Sino-Japanese War and had secured vast occupied territories in mainland China. For Japan, that current situation was the reference point. In contrast, for China and the United States, the situation before the occupation was the reference point. There was a discrepancy in the reference point, and it could be said that there was no other way to resolve the situation other than war. This phenomenon can also be observed in Russia's invasion of Ukraine and the Palestinian conflict.

Discussions on security are closely related to the SDGs. Prospect theory can also be applied to relations between developed and developing countries, and it can be said that we are in the process of searching for mutual reference points and finding compromises. The possibility of new partnerships between nations is emerging, but at the same time, there are also aspects that are giving rise to new conflicts. As with security, nice words alone will not work, but by introducing insights from modern Japanese history, it should be possible to understand the SDGs in a new way.