Tuesday Thought: This or that?

Two earlier postings covered these and those, the plurals of this and that, as demonstrative pronouns. Today's covers this and that as singular demonstrative pronouns. (Curiously, Fowler has no entries for them in this or that form.)

Their use in distinguishing time, order, or nearness is straightforward.

This is a pleasant meal.

That was a pleasant meal.

I prefer this to that.

But where this and that are demonstrative pronouns referring to an earlier sentence, matters can become more complicated. Consider this except from a piece in The Economist called 'Time to buy.'

But neither government bond markets nor commodities can in any sense be described as being near a bottom.

In short, this does not look definitely like the kind of low from which very good long-term returns can be made. That may be because the market has a lot further to fall; Morgan Stanley suggests that, if the superbear argument is correct, equities could drop a further 50%. But that will surely require some kind of economic news of the kind seen in the 20^th century.

The present tense (does not look) governs the use of this in the first sentence. And present tense (may be) would indicate the use of This in the second sentence as well, but having already used this in the preceding sentence, the writer switches to That to avoid repetition and possible confusion over the antecedent. Future tense (will surely require) would indicate the use of this in the third sentence too, but distance in time (seen in the 20^th century) indicates that, overriding tense.

Here are a few more from a piece in The Economist on chemical sensors, 'Gas, gas, quick boys.'

In this way the components of the sample separate from one another. Each component is puffed onto the nanotubes, where it sticks to the carbon atoms. This, in turn, causes the conductivity of the nanotubes to change--how much is a characteristic of each gas.

What is needed is a cheap way of detecting such gases and, having raised the alarm, of identifying which gas is involved so that anyone who has succumbed can be treated.

And that is what a team of chemical engineers at the Massachusetts Institute of Technology, led by Michael Strano (pictured on the left), think they have created.

Present tense dictates the use of This in the first pair. It should also dictate the use of this in the second.

Perhaps the writer felt that that would be more demonstrative than this. Or perhaps the writer preferred the word with an abrupt finish over the one with a hiss, a preference I'm beginning to note.

For more on that, view http://www.youtube.com/watch?v=Zo1XFz0kac0.