When I was a scientist, I didn't understand the distinction between that and which. In fact I didn't know there was a distinction; I thought if I didn't use which to refer to a person, everything was O.K. Eventually I heard that which was correct sometimes and that was correct other times. But I couldn't understand the explanations given -- something about essential and non-essential clauses or defining and non-defining clauses. I was referred to the definitive manual for writers, The Elements of Style, the third edition, by E.B. White and William Strunk, Jr. who say
That is the defining, or restrictive pronoun, which the nondefining, or nonrestrictive.
Somehow, this just wasn't clear to me. Yet Strunk and White go on to say
But it would be a convenience to all if these two pronouns were used with precision.
After reading many explanations of when to use which and when to use that, all of which seemed unclear, I finally figured it out while walking in Maine -- not from the explanations but from reading lots of examples. I then realized that the distinction was perfectly simple as long as it was explained in terms of sets.
After I became an acquisition editor at a scientific publishing company, I learned that this confusion over which and that wasn't unique to me. In fact, it seemed most people trained as scientists (and many non-scientists as well) were unclear about this. Yet I found that if I explained it to scientists in terms of set theory with Venn diagrams, they understood instantly.
So, if you are a scientist and you want your writing to be clear and easy to read but don't quite understand the distinction between which and that, please go to my page on that very topic.
You can learn even more about me by looking at my Resume.
© 1998 by Lorraine Lica