Can I be Certain of You?

In his comments on Philippians, chapter 1, verse 6:

And I am sure of this, that he who began a good work in you will bring it to completion at the day of Jesus Christ. Philippians 1:6 English Standard Version (ESV)

John Calvin says:

It is asked, however, whether anyone can be certain as to the salvation of others, for Paul here is not speaking of himself but of the Philippians. I answer, that the assurance which an individual has respecting his own salvation, is very different from what he has a...