I'm sorry, but can you be more specific? If your friend says that history repeats itself, what specific events is he talking about?

(I do hope this kind of comment is allowed on this sub, but since the OP was not very specific, I can't be expected to give a detailed answer with sources.)

This is an interesting theory question. My answer is of my own opinion, so others may disagree (certainly many historians with advanced theory training would disagree with some or all of it), but I will draw from the very most basic historical theory/methods to try to provide an answer. I do not think “history repeats itself” because it goes against what a professional historian does. Sure, events in the past may look similar. A common phrase among some lay people is that history “rhymes.” That may be true: Comparisons in history are acceptable when done in the right way. But the reality is that history does not repeat itself. There is no grand process of inevitable improvement, and there are no cyclical movements. There are no laws of history. All of these assumptions go against the basic historical method that historians attempt (however imperfectly) to follow.

Although certain moments may seem the same at first (and usually at only the most cursory, simplistic, “zoomed-out” glance), every moment in history is particular and unique. historians are trained to look at evidence contained in surviving primary sources and only draw conclusions from those sources. In an ideal world (rarely if ever is this possible), a historian attempts to gather all of the relevant sources that seem to answer to their research question. The historian reads/watches/views/listens to those sources, attempting to understand what each source tells us about our research question, why the document was created, what biases it may contain, and what context informed its creator’s thinking. At the same time, the historian should investigate other factors at play in the past that help them answer the research question: the unique milieu, the cultural understandings, social beliefs that people at the time held, and the personality characteristics of individuals living in the period. A historian attempts to leave the present world behind. They try to get into the minds of the people of the time: to know what they knew, to believe what they believed, to think what they thought, to be a member of the groups that they were a part of, and to react the way they reacted based on what they knew at the time. When all of these factors came together, they made an event/moment/belief/action possible and completely unique. Then, the historian should study what other historians have already written, said, and believed and should read relevant theory that may inform why historical actors behaved in certain ways. Finally, a historian should tell the world about their findings, publicly present the conclusions for inspection by their peers, who check to see if the author is correct. This is as close to “scientific” history as a historian can get, and as many theorists have pointed out, it is basically impossible to do for various political, social, cultural, and material reasons.

But I hope that you see that the process of doing professional history is essentially the exact opposite of “history repeating itself.” If someone is looking for “history repeating itself,” they already know the outcomes of certain events (which people in the past did not and could not know), and they look for evidence that backs up their preconceived conclusion, leaving out sources and evidence, trying to force evidence to fit a certain story-line when it doesn’t (a bit like trying to shove a square peg in a round hole), or assuming that people in the past believed the same things as those of another historical moment or in the present. As soon as unique sources, individual personalities, and historical contexts come into play...when a person follows the basic historical method, the idea that history repeats itself is completely debunked.