To understand Dogma we must first find out what truth is. All that "is" whether visible or invisible is true in itself but is in transitional form so we read, "All flesh is like grass, and all its glory like the flower of the field; the grass withers, and the flower wilts; but the word of the Lord remains forever." (1Pt 1:24-25) For example, there are many varieties of trees in the world which are "passing away" but the idea of "tree" as a principle, for or type in the mind of God is eternal.
Truth in relation to the human mind is a bit different. "Truth, as Aquinas said, is the conformity of the mind with what is, not the opposite, not the conformity of reality with whatever the mind wants it to be." (James V. Schall)
This is where difficulties arise. While the human mind is always searching for the truth it does not easily find it due to human limitations. Some truths we can reason to, and some people are better at reasoning than others, while other truths had to be reveled by God because they are beyond our reasoning power (e.g. The Incarnation of Christ). Further, truths are expressed in human concepts and words which always fall short of the reality. Does this mean they are not true? If I say the sun rises in the east and sets in the west while the astronomer states that we see it this way due to the rotation of the earth, does this mean that one statement is false and the other true? Or, are they both true but perceived from different perspectives? A further difficulty arises with the interpretation of Scripture. Protestants claim that Biblical Revelation attests itself. However, this is not self evident since among Protestants there are variations of beliefs with the formation of many denominations.
The Church, form the beginning has been concerned with teaching the truth. St. Paul in the first letter to Timothy exhorts him to teach the true faith as follows, " I repeat the request I made of you when I was on my way to Macedonia, that you stay in Ephesus to instruct certain people not to teach false doctrines or to concern themselves with myths and endless genealogies, which promote speculations rather than the plan of God that is to be received by faith. The aim of this instruction is love from a pure heart, a good conscience, and a sincere faith." (1Tm 1:3-5) And, at the end of the letter St. Paul states, "O Timothy, guard what has been entrusted to you. Avoid profane babbling and the absurdities of so-called knowledge. By professing it, some people have deviated from the faith." (1Tm 6:20-21) By "knowledge" St. Paul is here referring Gnosticism. As time brought about more disputes over doctrine, the Church has defined them as Dogmas or Truths of faith to be believed by all Christians.
What than is dogma? "A dogma is simply the stating accurately, in the best way we can, in the language we know, what we know [to be true]." (James V. Schall) Here is a some dogmatic statements:
"Souls who depart this life in the state of original sin are excluded from the Beatific Vision of God. (De fide)
Dogmas are truths contained in revelation or truths that have a necessary connection with them. This does not mean that we understand all the implications of these statements; we can surely gain ever deeper understanding of dogma and they can even be paraphrased in a better way, but the basic truth they contain remains. Pope Pius XII affirms this, "Even in these fundamental questions [dogmas], we may clothe our philosophy in a more convenient and richer dress, make it more vigorous with a more effective terminology, divest it of certain scholastic aids found less useful, prudently enrich it with the fruits of progress of the human mind. But never may we overthrow it, or contaminate it with false principles, or regard it as a great, but obsolete, relic." (Humani Generis #30) In this long historical process the Church is aided by the Holy Spirit as Christ attested, "I have much more to tell you, but you cannot bear it now. But when he comes, the Spirit of truth, he will guide you to all truth. He will not speak on his own, but he will speak what he hears, and will declare to you the things that are coming." (John 16:12-13
We read in the Catechism of the Catholic Church #89:
Do we need dogmas? "The normal person is interested in dogma. He wants to know the truth. But it is rarely presented to him in terms he can understand. Lacking the proper explanations, many likely go about listening to or concocting ideas that are far from the true understanding of what faith teaches. (Dorothy Sayers) So, the answer is Yes!