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Thomas Aquinas was an Italian Dominican friar, philosopher, Catholic priest, and Doctor of the Church. An immensely influential philosopher, theologian, and jurist in the tradition of scholasticism, he is also known within the latter as the Doctor Angelicus and the Doctor Communis.  He was the foremost classical proponent of natural theology and the father of Thomism; of which he argued that reason is found in God.

Furthermore, Thomas is distinguished for his eucharistic hymns, which form a part of the Church's liturgy.  The Catholic Church honors Thomas Aquinas as a saint and regards him as the model teacher for those studying for the priesthood, and indeed the highest expression of both natural reason and speculative theology.

Thomas Aquinas is considered one of the Catholic Church's greatest theologians and philosophers. Pope Benedict XV declared: "This (Dominican) Order ... acquired new luster when the Church declared the teaching of Thomas to be her own and that Doctor, honored with the special praises of the Pontiffs, the master and patron of Catholic schools."  The English philosopher Anthony Kenny considers Thomas to be "one of the dozen greatest philosophers of the western world".

Source: https://en.wikipedia.org/wiki/Thomas_Aquinas

1.  First Mover - In the world, we can see that at least some things are changing. Whatever is changing is being changed by something else. If that by which it is changing is itself changed, then it too is being changed by something else. But this chain cannot be infinitely long, so there must be something that causes change without itself changing. This everyone understands to be God.

2.  Causation - In the world, we can see that things are caused. But it is not possible for something to be the cause of itself because this would entail that it exists prior to itself, which is a contradiction. If that by which it is caused is itself caused, then it too must have a cause. But this cannot be an infinitely long chain, so, there must be a cause which is not itself caused by anything further. This everyone understands to be God.

3.  Contingency - In the world we see things that are possible to be and possible not to be. In other words, perishable things. But if everything were contingent and thus capable of going out of existence, then, nothing would exist now. But things clearly do exist now. Therefore, there must be something that is imperishable: a necessary being. This everyone understands to be God.

4.  Degree - We see things in the world that vary in degrees of goodness, truth, nobility, etc. For example, well-drawn circles are better than poorly drawn ones, healthy animals are better than sick animals. But judging something as being "more" or "less" implies some standard against which it is being judged.  Therefore, there is something which is best and most true, and most a being, etc.  From this [Aquinas] deduces that there exists some most-good being which causes goodness in all else, and this everyone understands to be God.

5.  Final Cause - We see various non-intelligent objects in the world behaving in regular ways. This cannot be due to chance since then they would not behave with predictable results. So their behavior must be set. But it cannot be set by themselves since they are non-intelligent and have no notion of how to set behavior. Therefore, their behavior must be set by something else, and by implication something that must be intelligent. This everyone understands to be God.

Source:  Copleston, Frederick (1993). Medieval philosophy : [from Augustine to Duns Scotus] ([Repr.]. ed.). New York [u.a.]: Image Books, Doubleday. pp. 341–342.

“To one who has faith, no explanation is necessary. To one without faith, no explanation is possible.” 

“To pretend angels do not exist because they are invisible is to believe we never sleep because we don't see ourselves sleeping.” 

“How can we live in harmony? First we need to know we are all madly in love with the same God.” 

“If, then, you are looking for the way by which you should go, take Christ, because He Himself is the way.” 

“It is requisite for the relaxation of the mind that we make use, from time to time, of playful deeds and jokes.”