On the eve of the Solemnity of the Immaculate Conception I want to put to rest a myth in Catholic Theology. St. Thomas Aquinas didn't deny the Immaculate Conception. If you ever hear this comment you will now have the tools necessary to defend the Angelic Doctor against those who would try to defame him using the Blessed Mother.
Read the article linked by Don Paco. It is very short and very clear. He simply shows the three intellectual phases of Aquinas' thought concerning the Immaculate Conception. I'm always discouraged when I even hear Dominicans repeat the myth. We should be better defenders of our brother Thomas.