Why is justification by faith such an important doctrine?

This article has been translated into the following languages:

Afrikaans العربية Български 中文 中國話 Deutsch Español فارسی Français Ελληνικά हिन्दी Hrvatski Bahasa Indonesia Italiano 日本語 Kiswahili 한국어 Magyar Polski Português Română Русский සිංහල Slovenčina Srpski Tagalog ไทย Українська اردو Tiếng Việt