A platform for learning, teaching, and practicing formal logic.
If you want to learn formal logic and don't have a teacher to guide you, you may want to start with one of the open-source logic textbooks, available here . If you are new to JustInfer, you may want to start with the tutorial videos, available here. If you just want to learn more about this site's capabilities, scroll down.
Students can enter justifications and see if there's a corresponding inference. Given the derivation system chosen in settings, only premissible inferences are allowed. This builds good habits for students and helps students learn how their derivation system works.
Try it nowCustomize symbols and rules of inference according to your system. The symbols chosen for the connectives rewrites well-formed formulas accross all problems on this website.
Go to SettingsAs an instructor you can create courses, upload problems, view student progress, and set up the derivation system for your course. As a student you can solve course derivations using the JustInfer system to ensure you are doing derivations in a proper way according to your professor's chosen settings. You must create an account to gain access to these features but accounts are free and easy to create.
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Currently, JustInfer is entirely free, offering everyone the opportunity to learn, practice, and teach formal logic without any charge, ads, or selling of personal data.
However, data storage and server costs make it infeasible to maintain completely free access to all of the site's capabilities.
The current plan is that future users would need to pay a one-time fee of approximately $10 to access course related features.
This would not affect users who have already created an account and enrolled in or created at least one course before this plan launches. You'll continue to enjoy free access to all course-related features indefinitely, including the ability to make and enroll in additional courses.
Moreover, all other parts of JustInfer, including logic textbooks, tutorials, practice problems, and custom settings, will remain permanently free for everyone! I am committed to keeping this an ad-free, privacy-respecting, and affordable platform for learning and teaching formal logic.
If you'd like to help me continue offering course capabilities for free, please consider supporting JustInfer through a donation.
Thank you for your understanding and for supporting JustInfer!