Complex sentence: His position simultaneously rejects the utopianism of Idealists and the "realpolitik" which eschews moral considerations and approaches international relations from a purely utilitarian perspective: a fallen world requires a realistic approximation of the dangers and pitfalls of international relations.
Split into simpler sentences: His position simultaneously rejects the utopianism of Idealists and the "realpolitik" which eschews moral considerations and approaches international relations from a purely utilitarian perspective. A fallen world requires a realistic approximation of the dangers and pitfalls of international relations.