Truly, doubting Thomas was an apostle, too.
But those who believe without seeing are blessed.
But Christians do share in the same Spirit and thus, share in the mind of Christ. Thereby we recognize one another, the body of Christ. Not that we agree on other things, we don't - but we all know Who He IS.
For as the body is one, and hath many members, and all the members of that one body, being many, are one body: so also [is] Christ. For by one Spirit are we all baptized into one body, whether [we be] Jews or Gentiles, whether [we be] bond or free; and have been all made to drink into one Spirit. For the body is not one member, but many. - I Cor 12:12-14
And so are the merciful.
Then there would be one church, rather than many. Everyone makes his own Jesus.
They all have the same name they call on. But everyone has a different idea what he is.