One interesting feature of the history of philosophy is how it is affected by purely verbal shifts. For instance, there was once almost universal agreement that "Every event has a cause" is a necessary truth. This later breaks down, and it would be difficult to find anyone who would agree to it without qualification today. But this is a matter of words shifting their meaning. Originally 'event' and 'effect' were virtually synonymous; literally, an event is something that comes from something else. It was the latinate form of the word 'outcome', and meant exactly the same thing. But over time (it began fairly early) the word 'event' breaks away from its connection with 'effect' and 'outcome' and takes on a more abstract sense of what happens during a stretch of time; that is, while it could be used in both senses, the 'outcome' usage slowly declines. There is a slow growth from talking about causation as the relation between events and their causes or antecedents to talking about causation as a relation between two events (which had originally been used to talk about time).
One of the things that is interesting about such things is that these verbal shifts set up sandbars that make it harder to read prior works accurately; someone who goes back and reads, say, Welton, on causes will run the danger of misunderstanding what Welton means when he says 'Every event has a cause'. There are many examples of this. For instance, 'conjecture' originally meant 'probable inference'. Bernoulli's classic treatise on probability was entitled, The Art of Conjecture. When Malebranche says we know that other minds exist by conjecture he is saying that we know it by probable inference. Hume in ECHU uses the word at least once as an explicit synonym of 'probability', and wherever you find it in Hume, this is what it clearly has to mean. Someone unaware of this, however, would be like to understand the term in our modern sense, in which it means 'guess', leading to any number of misunderstandings. Language is reason's finest instrument; but it is a slippery instrument, and a certain delicacy and art is required in order to handle it properly.
