Note: This post briefly outlines and compares both idealism and realism, in an international relations context and definition. My research on this topic is not at all substantive, so please feel free to let me know if I have misrepresented something or missed out on anything crucial. Happy to hear your thoughts. 

In an international relations context, there are typically two main approaches to foreign policy: idealism and realism. Both offer distinct perspectives on how nations should interact with each other and pursue their goals. Idealism emphasizes the importance of internal values and moral principles, therefore advocating for foreign policies that reflect these values to create an ultimately more just and peaceful world. On the other hand, realism focuses on national interests, security, and power, hence prioritizing strategic objectives and practical outcomes over ethical considerations. 

Idealism

The core of idealism focuses largely on the internal values, beliefs, and principles of a country. According to idealism, the foreign policy of a country should mirror these values - for example, if a country values conserving the environment, defending human rights, and reducing socioeconomic disparities domestically, it should aim to do the same on an international scale. Ultimately, idealists believe that to build a more peaceful and cooperative world over time, this approach of instilling, practicing, and ensuring the foreign policy embodies these inherent values is crucial. 

Let every nation know, whether it wishes us well or ill, that we shall pay any price, bear any burden, meet any hardship, support any friend, oppose any foe to assure the survival and the success of liberty - U.S. President John F. Kennedy

In summary, idealism reflects a country’s ethical and moral values.

Furthermore, here is an extract from the Council on Foreign Relations the objectives of idealism in an international relations context. 

Idealists believe in actively participating in global affairs to share the values they hold dear and shaping countries to reflect those values. That approach can entail cooperating with others or acting solo to address what idealists see as the world’s greatest problems. Note, however, that idealism is not the same as pacifism. Idealists can spread their beliefs around the world forcefully, pressuring or even invading other countries.

Realism

Contrary to idealism, realism approaches foreign policy from the perspective of interests rather than values. Realists prioritize core interests such as national security and the relationships with allies over the moral, ethical, and intrinsic values of a country. Hence, they have a larger focus on their international relations and foreign policy rather than the domestic policies of other nations. They emphasize what directly affects their nation and often overlook the internal actions of foreign governments. 

A country that demands moral perfection in its foreign policy will achieve neither perfection nor security - U.S. Secretary of State Henry Kissinger

A country adopting a realist approach to their foreign policy will often not intervene when its allies or nations with strong trade relations are acting against what the country believes in, i.e. human right violations. This would be largely to benefit and protect their core interests of national security and prosperity in their relations with foreign countries. 

Here is an extract from the Council on Foreign Relations regarding Realism in an international relations context.

Realists, meanwhile, don’t necessarily deny the importance of human rights or democratic governance. Rather, they just believe that the way to achieve peace and prosperity is by influencing how other countries interact with the world instead of trying to change those countries’ internal affairs. Rather than focusing on every humanitarian crisis, realists build power and influence to mold the world in their vision. Realist ends are achieved by forming strong alliances, developing military capabilities, or weakening rivals. Realists believe sharing one’s values abroad often has unintended consequences that can destabilize countries and regions.

Drawbacks of Idealism and Realism

Drawbacks of both idealism and realism also persist with each approach having their own limitations, particularly when they are actually applied to foreign policies. 

For example, countries only have so much power to influence other governments' actions. Even if idealists hope to influence other countries' policies based on their own values, it may not be practical to do so - regardless if the United States wishes to see democracy flourish in China or Russia, they do not have the power to influence the governments' actions and cannot exactly impose their democratic values and principles. Additionally, even with the best intentions to benefit another country, it just may not happen and, instead, yield unintended consequences. 

Similarly, with realism, there are drawbacks as a result of having a strong focus solely on core interests such as economic and security interests. For instance, realists could easily neglect their moral obligation to alleviate suffering around the world and intervene for the "greater good". They may also empower bad actors by not actually intervening to condemn certain actions, potentially exacerbating current conflicts. 

Debate Between Idealism and Realism 

In most cases, both idealism and realism will be present to some extent within foreign policies. However, the extent to which each of these is emphasized/ accommodated into the policy depends on the approach that the government chooses to take.