Comment by md_

I wonder if you read the linked Wikipedia entry, which includes:

> In political science, Duverger's law holds that plurality-rule elections (such as first past the post) structured within single-member districts tend to favor a two-party system.... In the course of further research, other political scientists began calling the effect a "law" or principle.

(Emphasis, of course, added.)

The article goes on to note counterexamples, to drive home the point that this is not, as you say, like a law of physics.

Perhaps a more constructive phrasing you could have tried would be something like,

"As noted in the linked article, there are many counterexamples, so while as you say first-past-the-post may encourage two-party systems, it doesn't preclude more parties from existing."

This would have been a more polite phrasing, one that shows you read and comprehended both my comment and the article I linked to, and one that would not exhibit the logical fallacies your original comment does (to argue that the existence of counterexamples precludes any causal relationship between first-past-the-post and two-party systems).

Hope that helps. Have a nice rest of the weekend.