While most historians have never heard of him, Maurice Mandelbaum, a philosophy professor at Darmouth University, was the founding father of the analytic philosophy of history. When Mandelbaum launched his professional career in the 1930s, the “philosophy of history” meant essentially what we would today call “speculative history”, that is, grand theorizing about the ultimate cause and course of history. Mandelbaum therefore called his new field of interest “historiography” which of course today has multiple meanings such as the history of history, the methods of history, of even the philosophy of history. In other words, all of these terms are interwoven and confused because they are used differently by different people over time. At any rate, Mandelbaum was aware of the European, largely German traditions of theorizing about history that dated to the mid-19th century. He knew that the American historians were about a hundred years behind their German colleagues when it came to thinking about the nature of history.
In 1938, responding to new subjectivist epistemologies by the Americans Charles Beard and Carl Becker, Mandelbaum wrote The Problem of Historical Knowledge (New York: Liveright), a defense of objective historical truths, which, to my mind, remains the best or at least most lucid philosophical defense of the topic ever written. For the generation to follow, analytic philosophy of history remained focused on a few problems, primarily these were (1) epistemological problems, specifically the debate about subjective versus objective facts, (2) problems of causation: what does it mean for something to be the cause and another to be the effect?, (3) problems of the nature of historical knowledge, specifically the “covering laws”, that is: is historical knowledge particular or general, does a specific historical event demonstrate deeper underlying laws or structure of history, like a particular experiment in the lab demonstrates deeper laws of physics.
In an article on Mandelbaum from 1989, Christopher Lloyd gives a worthy description of some important elements of Mandelbaum’s views. According to Lloyd, Mandelbaum believed in the correspondence theory of truth,
“This says that the order of events that is found in nature and history really does characterize the mind-independent events of the world, which are not transformed by the mind in the act of knowing. Events have an existential relation of causal dependence on each other, and facts are statements about events, so the relevance of facts to each other is not dependent on some epistemology, value system, interpretation, or theory. Rather, historical relevance, interpretation, and synthesis are based on the discoverable causality of the external world.”
By mind-independent, Lloyd means that the world exists independently of one’s mind; that the world is not the product of our imaginations, that it has real, physical existence. This is, I think, an important point for those who wish to stress the difference between history and the past. This distinction is sometimes lost on non-historians, and, indeed, on some historians. In Mandelbaum’s thought, the past exists regardless of whether historians are around to analyze it. History, however, is the product of our minds’ efforts to extract pattern and meaning from the past.
Lloyd continues Mandelbaum’s point here:
“However, historical social processes, although real, consist of an infinitely large number of components and do not form a completely integrated set in which every component is causally interrelated to all others. Therefore, he argued, not all existential relations are necessary ones and any form of historical holism or monism is ruled out. Descriptive causal analyses have to be pluralistic and partial because of the lack of integration. And contra phenomenology, historians do have to analyze the structure of supposedly holistic epochs and processes which in reality do not have a unity existence.” 
One part of this view, what is sometimes called historical pluralism, also appears in the works of the philosophy of history Frank Ankersmit. It is something that I have repeated in my book, Creative Historical Thinking with the observation that one explanation of the past is fine, but a plurality of explanations is better. History, I argue, is not one thing, one story, from one objective perspective. Rather, history is stronger and better developed when it is written from multiple angles for multiple purposes, teasing out more meaning. Historical pluralists like myself argue that we need histories that disagree with each other, that disagreement is natural when the past is analyzed from different angles.
I wasn’t away of Mandelbaum when I wrote my new book, and I have a lot more of him to read. He appears to have anticipated many of the developments late 20th century philosophy of history, although it may be said just as well that what developed after his first book was a response to his work. I wish this were true. All too often, I fear, major books on the philosophy and methods of history were only casually informed by their predecessors’ work. Analytic philosophers of history like Gallie and Dray knew Mandelbaum’s work well, but later historians who wrote about methods largely ignored analytic philosophy of history and its questions of knowledge, causation, explanation, and covering laws. I never encountered Mandelbaum in graduate school, and was instead given Peter Novick’s That Noble Dream. But newer is not necessary better. Better than Novick on the history of the American historical profession is Higham and Krieger (1965); better than Novcik and E.H. Carr and most anyone of note in the genre of philosophy and methods of history is the original father of the philosophy of history, Maurice Mandelbaum.
The golden age of the analytic philosophy of history, from the 1940s through the 1960s, was replaced by postmodern theorizing about history. Mandelbaum continued to publish valuable contributions to the analytic philosophy of history into the 1980s, before his death in 1987. None were as important as his first book, however.
 Christopher Lloyd, “Realism and Stucturism in Historical Theory: A Discussion of the Thought of Maurice Mandelbaum” History & Theory 28:3 (1989), 296-325, specifically 302.