I would not agree that we cannot define development. It is a complex subject, but one that can be defined. Instead, I would say that it is much more difficult to determine the identity of the most important contributor to development.
I have seen a very good definition of development in a textbook I use for teaching human geography. This is Fouberg, et. al. Human Geography: People, Place, and Culture 9th Edition. On p. 321, the book says that development
means improvements in technology and production as well as improvements in the social and economic welfare of people.
This is, in my view, a very clear and usable definition of development.
Of course, this does not mean that it is easy to know development when we see it or that everyone will agree on what development looks like. In fact, it is easy to argue that our definition of development is biased because we believe that our (rich) society is superior to other societies. The definition of development given above talks about improvements in people’s social welfare. It is hard to define exactly what constitutes improvement in social welfare without bringing in cultural biases. For example, many scholars use the education of women as a measure of development. Clearly, there are people in other countries who would not think that educating more women constitutes progress. Similarly, most definitions of progress include democratization. The Chinese government, to take one example, would not agree that this would improve social welfare. Finally, there are even those who question the value of economic development. This can be seen in the push for the use of “gross national happiness” as an alternative measure of development. Thus, while we can give a definition of development rather easily, it is not completely clear that this is a definition on which everyone can agree.
What is even more difficult is identifying the most important contributor to development. If this were obvious, more countries would surely be developed by this time. In a sense, it is easy to say that economic wealth is the most important contributor to development. When a country starts to gain wealth, its other indicators of development tend to rise as well. More wealth means more children can go to school and literacy rates rise. More wealth means better medical care and maternal and infant mortality decline. More wealth even tends to bring about greater demands for political freedoms, raising the degree to which governments democratize. In these ways, we can say that economic wealth is the most important contributor to development.
The problem is that this is not very helpful. Almost all countries want wealth. However, they do not know how to get wealth. Whatever causes countries to become wealthy, then, could be defined as the most important contributor to development. There are a number of possible answers as to what causes countries to become wealthy. It could be education. When more people are educated, they are able to get better jobs and to do things that create more wealth. It could be the rule of law and good governance. When people know that the government will not arbitrarily take away their property or demand large bribes at every step in the process of creating and maintaining a business, they will invest more money and labor in creating businesses. This will help the country prosper. However, it is not easy to know how to get education, good governance, and the rule of law without first having wealth. This means that it is very hard for us to identify how a country can gain wealth and, thereby, development.
Thus, I would argue that development is relatively easy to define, but that it is very hard to know what factor is the most important contributor to development.