If you're having trouble applying →I, click on the statement below that best describes the problem you're having.
I can't select →I from the Intro Rules menu.
If a rule is not appearing in the ToolBox menus, then that rule is not available for the currently loaded problem. Rules are available only for derivation problems that follow the presentation of the rule in the text, regardless of what problems you may have completed previously.
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I can't select the consequent of the conditional I want to derive in the Fitch
First, make sure that there isn't a problem with your mouse by clicking to change applications or browser windows. If your mouse is working properly, try clicking on different parts of the formula. If you are still unable to select the formulae no matter where you click on them, try exiting the CPL and reloading the problem. If the problem persists after reloading, please inform your instructor.
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I can't select the conditional I want to derive in the Goal Tree.
First, make sure that there isn't a problem with your mouse by clicking to change applications or browser windows. If your mouse is working properly, try clicking on different parts of the formula. If you are still unable to select the formula no matter where you click on it, try exiting the CPL and reloading the problem. If the problem persists after reloading, please inform your instructor.
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When I clicked the Apply Rule button when attempting to apply →I backwards, I got an error message saying that the goal formula was not a conditional.
Conditional introduction can only be used to derive conditionals. Check carefully to make certain that the formula you are selecting in the Goal Tree really is a conditional. Any conjunction will appear in the Goal Tree in the form ( φ → ψ ).
If the formula is definitely a conditional but you still get the same error message when applying the rule, try exiting the CPL and then reloading the problem. If the problem persists after reloading, please inform your instructor.
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When I clicked the Apply Rule button, I got another error message or nothing happens.
Make sure that you have selected the correct rule in the ToolBox, and that you have selected either the last line of a subderivation in the Fitch or a conditional in the Goal Tree. If your selections are correct, the instantiation pane of the ToolBox will be auto-filled with the antecedent, the consequent, and the conditional, respectively.
If the rule instantiation is auto-filled, but you continue to experience problems when attempting to apply the rule, try exiting the CPL and reloading the problem. If the problems persist after reloading, please inform your instructor.
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I'm trying to apply →I forwards to more than one line.
Conditional introduction is applied to a single line, the last line of a subderivation. The formula derived will be the conditional with that formula as the consequent, and the assumption that opened the subderivation as antecedent.
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I can apply the rule successfully, but the wrong conditional is derived.
Check the justification for the new line in the Fitch to make sure you applied the rule in the way you expected. The formula derived will be conditional with that formula on the line cited (the last line of a subderivation) as the consequent, and the assumption that opened the subderivation as antecedent.
Show me where to look for the justification
If the conditional you wish to derive is present in the Goal Tree, you can always apply →I backwards to this conjunction in order to eliminate the possibility of making incorrect selections in the Fitch.
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