GRAMMAR DETAIL

〜も同然だ

virtually the same as

Strongly evaluates two things as effectively no different in result or condition even if they are not outwardly identical.

Examples

根拠を示さずに結論だけを押しつけるのは、議論を拒むのも同然だ。

Imposing only a conclusion without presenting evidence is virtually the same as refusing to debate.

このまま放置するのは、問題を認めるのも同然だ。

Leaving it this way is virtually the same as admitting the problem.

返事をしないのは、誘いを断ったのも同然だ。

Not replying is virtually the same as declining the invitation.

Structure: Attach も同然だ to a noun, a verb's ta-form, or a clause nominalized with の to strongly judge a result or condition as virtually equivalent to it.
Basic usage: 返事をしないのは、誘いを断ったのも同然だ。 means that not replying is effectively the same as declining the invitation.

Difference between 同然 and 当然
- 勝ったも同然だ judges the situation as virtually a victory. 勝って当然だ treats winning as expected or only natural, so the two judgments have different bases.