The phrase "expresses this idea" is correct and usable in written English.
You can use it when you want to indicate that something, usually speech or writing, presents an idea or point of view. For example, "His speech expresses this idea that all people should have equal access to education."
When Isaac Newton expressed this idea, he also exemplified it: he was effectively quoting 12th-century philosopher Bernard of Chartres.
Mr. Schwarzenegger, who was lounging on Maui's beaches with his family when he expressed this idea, said that lawmakers were spending too much time in Sacramento writing too many "strange bills".
And @SoSadToday was the online voice who expressed this idea better than anyone else, the one whose followers found in her comments what they'd been meaning to say.
Structuralists sometimes express this idea by saying that numbers have no internal properties or that their only properties are those they have because of the relations they bear to other numbers in the structure; e.g., 4 has the property of being between 3 and 5.
Fisher also expressed this idea in a more mathematical language in the so-called geometric model (Fig. 2).
Another way of expressing this idea is that we are good lightning chess players but terrible long-term chess players.
One could try to express this idea with Einstein's remark about the need to "free oneself from the idea that coordinates must have an immediate metrical meaning".
Another way of expressing this idea is in the Neoplatonic principle, going back at least to Iamblichus, that everything is in everything (panta en pasin).
In 1908 Duhem expressed this idea by a simile: scientific progress is like a mounting tide, where waves rise and withdraw, but under this to-and-fro motion there is a slow and constant progress.
