If a painter were to make an oil painting of a haystack, a viewer could look at it and see a haystack. If a different painter were to make an oil painting of a haystack a year later, a viewer could still admire the newer painting. If a painter were to make an acrylic painting of a haystack a century later, a viewer could look at it and still admire it. Or a viewer might prefer the first haystack ever painted. But yet another artist could depict a haystack and a viewer might be bored by the lack of originality (so many haystacks!) or vitalized by the freshness the younger painting brings to a haystack, contingent on the artist’s skill and the viewer’s preferences.
Philosophy is the same. One philosopher might think and write about the contingency of “truth” through the lens of human unreliability, and seventy years later another philosopher might write about the same thing but with different syntax, sentence structure, and paragraph development. The latter may or may not be familiar with his predecessor who addressed the frailty of “truth” seven decades earlier, but their idea need not be plagiarism or even derivative. Philosophers like artists bring many tools to articulate ideas, and if the “thought-objects” end up being similar, then different grammars will at least shed different light on the idea, just as one haystack is not made defunct by the existence of an earlier or later haystack: we judge each painting according to its own merits contingent within certain contexts. I paint haystacks, too.