Should I use singular or plural here?

Which is correct and why?:

I like to adopt abandoned things. This, and the fact that my wife works for an animal charity, appear to be why I have six dogs.

I like to adopt abandoned things. This, and the fact that my wife works for an animal charity, appears to be why I have six dogs.

I’m not sure because I could talk of both factors as a single set, or a single mereological object, or, alternatively, I could be talking of both factors as two things.

Solution 1:

A plural verb-form here doesn't work well. There is a fixed phrase

• This appears to be why ...

for instance

• This appears to be why Ian Rapoport was suspended
• This appears to be why Senate Majority Leader Mitch McConnell reconvened the Senate on May 4
• This appears to be why they improve insulin sensitivity and reduce body fat ...
• Indeed, this appears to be why particle theorists were so off base in their prediction

(examples from 144 000 Google hits), while

• these appear to be why

has one relevant hit. This apparently reasonable variant (there could easily be several reasons involved) seems unwelcomed, perhaps because it sounds incongruous. An easy override explanation by those using notional agreement is to see the multiple reasons as adding up to one compelling situation (with anaphor 'This'). But to my ears, OP's second variant doesn't sound too well-formed either.

As

• Jack and Jill appear to be getting on well, considering and
• This, and the fact that my wife works for an animal charity, appear to be the major reasons why I have six dogs

are idiomatic and obviously grammatical, it looks like acceptability or otherwise here isn't a matter of grammar.

Adding padding to the original as in the last example above, or it-clefting:

• I like to adopt abandoned things. It appears that this, and the fact that my wife works for an animal charity, are the reasons why I have six dogs

restore idiomaticity.

Solution 2:

I think it'd be better not to use the commas in the first place as follows:

I like to adopt abandoned things. This and the fact that my wife works for an animal charity appear to be why I have six dogs.

Here, This and the fact that my wife works for an animal charity are syntactically combined into a plural subject, thus requiring plural verb appear.

Not all writings are well thought out, however, so some writers might start with This and the fact that... without a comma after This, thinking that they're presenting a plural subject, only to add a comma before plural verb appear to somehow separate the that-clause from the following main clause:

I like to adopt abandoned things. This and the fact that my wife works for an animal charity, appear to be why I have six dogs.

Some might leave it as is, resulting in a bad writing, and some might try to fix the bad writing and, as an afterthought, add another comma after This to make it look better:

I like to adopt abandoned things. This, and the fact that my wife works for an animal charity, appear to be why I have six dogs.

Now they didn't intend to make and the fact that my wife works for an animal charity a supplement, but nevertheless ended up making it look like one by adding commas around it. The problem is, then, they don't realize they essentially made it look like a supplement, or they might even be thinking that it's not a supplement even though it has commas separating it from the rest of the sentence.

But the reader has no way of figuring out what the intended structure was, other than relying on the commas, necessarily leading to confusion.

In order to avoid this confusion, you can either not use the commas at all as suggested in the first rewrite above or rewrite the text altogether as follows:

I like to adopt abandoned things. Because of this and the fact that my wife works for an animal charity, it appears, I have six dogs.