Help. the usage of the word "reason" in this sentence.

I do not understand the usage of the word "reason" in this sentence. "You can lead a horse to water, they reason." I think its supposed to be something like you can lead a horse to water but you can't make him drink. How is the word "reason" was used in this sentence? https://preview.redd.it/3uwvrc55xvp61.jpg?width=1440&format=pjpg&auto=webp&s=28df2c4368ff7b603b586d7996cc0dbcb203a6d0 submitted by /u/EveningMysterious689 [link] [comments]

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