Thank you for the quick, and disappointing (as expected) answers.

The problematic definition:
$( Define Tick, Predicate ` ph '. <-> ( ph ^. 1 ) ` $)
df-bl.tick $a |- ( ph '. <-> ( ph ^. 1 ) ) $.

Because tick is used as syntactic sugar,  I can do without it.
Unfortunately, I have other theorems whose proofs mmj2 won't unify, so were 
also proved using MM-PA. 

I forked the set.mm GitHub repo (brlarson) in preparation for contributing 
my small bit to the community.

On Friday, February 2, 2024 at 5:49:07 AM UTC-6 [email protected] wrote:

> That error message means that the theorem df-bl.tick has a statement that 
> does not match the expression  |- ( A = B '. <-> ( A = B ^. 1 ) ) that you 
> have provided. It's difficult to say more without seeing the rest of the 
> code (and in particular, the definition of `df-bl.tick`).
>
> Q1: No, this is a fatal error, the proof is not correct as written. One 
> way you can try to clear things up is to delete the statement (just the |- 
> ( A = B '. <-> ( A = B ^. 1 ) ) part) and let mmj2 fill it in for you. The 
> only steps you can't delete are the hypotheses IIRC.
> Q2: I think there isn't any centralized listing other than the source 
> code: 
> https://github.com/digama0/mmj2/blob/1cd95c1fe4435899c8575644fccb412dd77d79e4/src/main/java/mmj/pa/PaConstants.java#L2790-L2794
>  
> . In general you can search the repo for uses of the constant which might 
> have some additional clues about it, but most of them carry a decent amount 
> of explanation text which will be more helpful than looking at the code.
> Q3: Yes, because set.mm only accepts completed proofs, and mmj2 will not 
> produce a completed proof (a block starting with $= at the bottom of the 
> file) until all unification errors are fixed and missing steps are filled 
> in.
>
>
> On Thu, Feb 1, 2024 at 10:59 AM Brian Larson <[email protected]> 
> wrote:
>
>> I much enjoy using mmj2, and am often amazed at how its unification 
>> deduces a theorem to solve qed when I think I've got a couple more steps to 
>> go.  However, sometimes I get failure in its final unification check.
>>
>> The error message:
>> E-PA-0410 Theorem bl.tkeq: Step 100: Unification failure in derivation 
>> proof step df-bl.tick. The step's formula and/or its hypotheses could not 
>> be reconciled with the referenced Assertion. Try the Unify/Step Selector 
>> Search to find unifiable assertions for the step.
>>  ---------------------------------------------------------
>>
>> The culprit: 
>> 100::df-bl.tick     |- ( A = B '. <-> ( A = B ^. 1 ) )
>>
>> '. and ^. are modal logic operators which determine in which "world" 
>> variables and predicates made with them should be evaluated:  A must equal 
>> B one thread period hence.
>>
>> Both operators can be applied to wffs or classes:
>> $( Define ` ( ph ^. A ) ` as a wff $)
>> wts $a wff ( ph ^. A ) $.
>>
>> $( Define ` ( A ^. B ) ` as a class $)
>> clts $a class ( A ^. B ) $.
>>
>> $( Define ` ph '. ` as a wff $)
>> wtick $a wff ph '. $.
>>
>> $( Define ` A '. ` as a class $)
>> ctick $a class A '. $.
>>
>> For other theorems which encountered this problem, I used MM-PA, and then 
>> included such theorems in the ProofAsstUnifySearchExclude list.
>>
>> Q1)  Is there some clever RunParamFile setting which will avoid the error?
>> Q2)  Where can the list of error codes like E-PA-0410 be found?
>> Q3)  Will the mmj2 check preclude such theorems from acceptance into 
>> set.mm?
>>
>>
>> --Brian
>>
>>
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>

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