The objection we seem to hear most often is the fact that we pray to Mary, when the Bible plainly says, (1 Timothy 2:5) “For there is one God, and one mediator of God and men, the man Christ Jesus.” But all Christians pray for one another as members of Christ’s body, just as we’re taught to do in James 5:16. If we can intercede for one another without intruding on Christ’s role as the one mediator, why can’t we ask for our Blessed Mother’s help as well? Given that Mary is the mother of God, a better question might be, why not ask for her prayers?
Part of the confusion no doubt stems from a misunderstanding of the difference between the verb and the noun. To pray is simply to ask for something (“What, pray tell, are you doing?”), although it is of course most commonly applied to an entreaty directed at God. Catholics do pray to Mary, but the thing we’re asking for is her intervention (the more accurate term, which Catholics use, is “intercession”). Only God can grant the kinds of things we’re asking Mary to obtain on our behalf, but with our Blessed Mother supporting us, so to speak, we stand a far greater chance that our prayer will be answered in the way we would like. St. Thomas Aquinas explained this in his Summa Theologica, Second Part of the Second Part, Question #83, Article 4.
It’s also important to make the distinction between veneration (dulia) and worship (latria). To venerate is to acknowledge with profound respect or reverence, whereas worship is the kind of ardent love and devotion that belongs only to a deity. We venerate the saints, and Mary highest among them (hyperdulia), but we worship only God.
The second most common assertion (in my experience) is sort of a two-parter: Jesus had brothers, therefore the concept of Mary as perpetual virgin can’t be true. But did Our Lord in fact have siblings? We read in a number of places throughout Holy Scripture of Jesus’s “brothers”, and many people take those citations at face value. This is a mistake, because ancient Hebrew and Aramaic (our Lord’s native tongue) have no word for brother in the genetic sense of the term—or, for that matter, aunt, uncle, or nephew. All close friends and relatives were referred to as either “brother” or “sister”. There’s an excellent example of this linguistic shortcoming at Genesis 14:12: “And Lot also, the son of Abram’s brother, who dwelt in Sodom, and his substance [was taken].” Two verses later, we read, “Which when Abram had heard, to wit, that his brother Lot was taken …” The word brother was used in place of nephew, a term which didn’t exist in ancient Hebrew.
Nor are James and Joses, the two “brothers of Jesus” referenced at Mark 6:3, His actual siblings, because they are in fact the sons of another Mary (see Matthew 27:56). If everyone said to be Jesus’ brother was in fact born of the same Mary as Our Lord, he would have had between 80-90 in his family: there were 120 people gathered in the cenacle at Acts 1:14-15, minus “the women” and “the apostles, the remainder of whom are referred to as Jesus’ “brothers”.
It’s often pointed out that Jesus was also called Mary’s “firstborn”, but this is because first-borns enjoyed a special status under Jewish law which entitled them to certain property rights. It doesn’t mean that she had any other children after Him. If a male child was the sole offspring of a married couple, he would still always be referred to as their “firstborn” for that very reason.
“And [Joseph] knew her not until she brought forth her firstborn son” (Matthew 1:25), the argument continues, therefore Joseph surely had relations with her after Jesus was born. But the word “until” does not necessarily imply a change in status, and Scripture supports this: In Acts 8:40, “[Philip] preached the gospel to all the cities, until he came to Caesarea.” Surely he didn’t stop preaching at that point. Deuteronomy 10:8 also has the tribe of Levi serving the Lord and blessing in His name “until this present day,” but no one seems to doubt that they continued their duties after that passage was written.