In order to answer this question, we must first be clear as to what it means. The wording of the question might lead us to believe that Schumpeter has presented a classical doctrine of democracy and that we need to defend his vision from his critics. However, this is not what is really going on in this question. Instead, Schumpeter describes a classical doctrine of democracy that has been propounded by earlier thinkers and he criticizes that doctrine harshly. The question is asking us, then, to argue against Schumpeter and for the classical doctrine of democracy.
In defending the classical doctrine of democracy, we will need to look at Schumpeter’s criticisms. We will examine them one by one and try to defend the classical doctrine against them. The first criticism that Schumpeter makes is that there is no such thing as a common good that all people can agree on. Schumpeter says that classical doctrines are wrong when they argue that people in a democracy can rationally agree on what is best for them. One way to argue against Schumpeter here is to say that essentially all people agree on a basic vision of the common good. We could argue that we all agree that people should have rights such as the right to vote and those rights enshrined in the Bill of Rights. We could argue that we all agree that everyone who is willing and able to work should be able to have a certain standard of living that is not impoverished. We may disagree on details about these things, but we generally agree on the basic vision of what the common good is.
Schumpeter also says that we will never agree on how to achieve the common good. Here, too, we can say that we do agree on a very basic level about how to achieve the common good. We can all agree that the way to achieve the common good is through democracy. We may not agree on the specific steps that need to be taken, but we can agree that those steps must be arrived at through democratic processes.
Schumpeter then goes on to argue that classical doctrines of democracy are wrong because democracy does not always produce the best outcomes. He argues that there are times when undemocratic governments make decisions or implement policies that are better than the decisions or policies of more democratic governments. One way to dispute Schumpeter’s argument is to say that, at a fundamental level, the process is more important than the result of any particular political decision. Let us think about this by thinking about slavery. Imagine that you are a particularly fortunate slave. You have an excellent master who makes great decisions. Your master does not abuse you. He provides you with a comfortable material existence. He ensures that you will not be poor in your old age or neglected when you are sick. He makes decisions that are better than those that you make for yourself. Most people would still argue that being enslaved is fundamentally worse than being free. Even if you would make worse decisions than your master, at least they would be your decisions. The worst decision that you make for yourself (we can argue) is better than the best decision that is forced upon you. Therefore, democracy is the best form of government even when democracies make bad decisions.
In these ways, we can argue that Schumpeter is wrong to say that the classical doctrine of democracy is fatally flawed.