Having grown up outside of the Catholic Church, many people tend to think that the intercession of the saints is something that I may have had a hard time accepting, as many converts do. However, since I was raised in a very “catholic-minded” Anglican faith, this was something that we already practiced. But, as I am a convert, I am often called upon by others to act as an apologist of sorts and to defend my beliefs in Catholicism. So, it is, nonetheless, a topic that comes up frequently.
First, let's tackle this biblically, because that’s what the protestants would want to see. We must look start by looking at James 5:16b “The prayer of a righteous man availeth much.” This is the cornerstone of the argument for the intercession of the saints. Our protestant brethren see this as the reasoning for asking those more grounded in the faith to pray for them, maybe a pastor or a deacon or elder in their community. We, as Catholics, take this a step further... for who is more righteous than a saint in heaven? They have already proven themselves and passed the litmus test of the faith.
So now we must solidify the Catholic rationale for extending the prayer of the “righteous man” to include those in the heavenly courts. To do this we will use two passages of scripture. First, Hebrews 12:1, “...since we are surrounded by so great a cloud of witnesses...”. “Surrounded?”, by a “Great cloud of witnesses”? So that means that the saints in heaven must be somehow (yet on a different plane) surrounding us? So... they can interact with us? Pray for us? [This notion is sure to make your inquirer/doubter stumble and reconsider a little.] Now add in this second thought from scripture, that in Revelation 7:15 it speaks of the elders surrounding the throne of God praying unceasingly. Now add in the lines from the 4th Chapter of the same book, where the 4 creatures and the elders are singing the “Holy, Holy, Holy” and the “worthy is the lamb” night and day without ceasing. By this passage we can assume that all that we do in heaven is prayer and praise. So why not pray for those on earth!
Finally, comes my favorite way to explain the intercession of the saints. I promise you that no protestant, no matter how anti-Catholic they say they are can deny this... When someone dies, say a parent, or a grandparent… someone close... we encourage the living to “speak to them in heaven” to know “they are looking down on us”. Some even say (incorrectly) that we have “gained an angel looking over us”. Now if those people are able to converse with the recently departed, or know that “grandma is looking out for us”, then either they actually believe in the intercession of the saints for the living, or they made up a line to make little Johnny feel better in his time of grief. I bet you, they don’t even know it, but they already believe in, and are subconsciously participating in the intercession of the saints.