Can you help understand the difference between soul, spirit and conscience?

What is Soul?

The Catechism of the Catholic Church teaches that the human person, created in the image of God, is a being at once corporeal and spiritual (CCC 362). The reason behind this is the unity found between the body and the spiritual soul that animates it (CCC 364). From this we can come to the conclusion that the soul is what gives life to the body, the life principle. Without the soul the body is nothing more than an inanimate object. If anyone (human beings) or anything (plants, animals etc) is alive then the body is united to a soul. 

It is to be understood that the human soul is unique and different from that of a plant or an animal. In man, the soul has not only vegetative powers (as plants have) and sensitive powers (as animals have) but also rational powers. This is why human beings can understand abstract notions like morality and justice while other living beings cannot. 

The Church teaches that every spiritual soul is created immediately by God – it is not “produced” by the parents – and also that it is immortal: it does not perish when it separates from the body at death, and it will be reunited with the body at the final Resurrection. – CCC 366

What is spirit? 

In normal circumstances both soul and spirit mean the same and can be used interchangeably. But there are also instances where soul and spirit are distinguished from each other like what St.Paul does while writing to the Thessalonians. 

“May the God of peace himself sanctify you entirely; and may your spirit and soul and body be kept sound and blameless at the coming of our Lord Jesus Christ.” – 1 Thessalonians 5:23

Here when soul is portrayed separately, it means that which gives life to a body while “spirit” when contrasted with “soul” simply means those aspects of human life and activity that transcend our bodily limitations and so open the soul toward the supernatural life of grace (spirituality). It is worthwhile to look at what the CCC talks about soul and spirit.

In Sacred Scripture the term “soul” often refers to human life or the entire human person. But “soul” also refers to the innermost aspect of man, that which is of greatest value in him, that by which he is most especially in God’s image: “soul” signifies the spiritual principle in man. – CCC 363

“Spirit” signifies that from creation man is ordered to a supernatural end and that his soul can gratuitously be raised beyond all it deserves to communion with God. –  CCC 367

What is conscience? 

St.Thomas Aquinas in his work Summa Theologiae defines conscience as the “application of knowledge to activity”. There are two things which need to be understood: application of knowledge and activity. Application of knowledge refers to judging whether an actual or potential action of mine (the activity) is or was good or bad, obligatory, forbidden or optional. The knowledge used here is nothing other than the law of God inscribed in our hearts and it is the internal rational capacity that helps us in doing so. Therefore conscience is a part of the human soul and is one of the characteristics which makes it (the human soul) unique. 

According to Catechism conscience is man’s most secret core or the sanctuary where he is alone with God whose voice echoes in its deaths. It is where the law of God is inscribed in man. It is the voice that calls him to love and avoid evil. (CCC 1776 – paraphrased)