The Logic Resource Center

Public Alpha

Systems

Public Alpha

Disjunction Introduction

The classical principle of logical addition. If something is true, then so is the claim that either it is the case or some arbitary other condition obtains - this is the idea behind Disjunction Introduction.

Constants: ∨
Systems: LRC_F The Logic Book LRC LRC_P LRC_O

Start a Problem →

Disjunction Introduction

i.

ϕ

ii.

ψ∨ϕ

∨I: i

i.

ϕ

ii.

ϕ∨ψ

∨I: i

Forward

Select an available formula
Specify the aditional disjunct
Specify the side on which you want to add it
Click "Apply"

Backward

Select a goal disjunction
Select a side
Click "Apply"

Preview shown for the Point And Click derivation type in the The Logic Book system