Several of the Treaties on European Union have contributed the development of European integration. The most noticeable agreements are the Single European Act and the Treaty of Maastricht. The treaties have provided the objectives and policies in political, economic, monetary integration among member countries.
The Single European Act was redefined from the Treaty of Rome. Its aim is to form a supranational political and economic integration among European countries. In this treaty, a common foreign policy was created through the encouragement of political co-operation. The creation of a single market had been introduced to achieve the economic goal. Including, the decision making process has been improved - the abolishment of unanimity and new majority rule. It has been signed in 1986 and entered into force in 1987.
The treaty on European Union focused on strengthening the legitimacy and effectiveness of the institutions and brought new areas of cooperation that marked a key stage in the process of European integration. The creation of the second and third pillars in particular marked a significant step forward, but these were explicitly intergovernmental.
The developments after Maastricht illustrate a theme that had been largely neglected by governments and analysts until then: the importance of legitimacy for the process of European integration.
The Treaty of Maastricht has been stemmed from the previous treaties - Paris, Rome and Single European Act. The original objectives - a single market and its political ambitions - have been further in this treaty. "It introduced the development of European integration with the five key goals:
- Strengthen the democratic legitimacy of the institutions
- Improve the effectiveness of the institutions
- Establish economic and monetary union
- Develop the Community social dimension
- Establish a common foreign and security policy
It has been signed in 1992 and become enforced in 1993".
From my opinion, the Treaty of Maastricht is the essential milestone for European integration. The treaty has been regarded as "the Maastricht Treaty creates the European Union". "The aim of this treaty has derived from the external and internal changes. By external events, the collapse of communism in Eastern Europe and the outlook of German reunification led to a commitment to reinforce the Community's international position toward a common foreign, policy, security and defense. At internal level, the Member States intended to complement the progress started by the Single European Act."
The article 2 of the Treaty of the European Union affirms that this Treaty marks a new stage in the process of creating an ever closer union among the peoples of Europe.It has the principal in major establishments of European Union and expands the integration in various areas. One of the core foundations is the Three Pillars which are the structure of the European Union. It is comprised of the European Community (EC), the Common Foreign and Security Policy (CFSP) and the Justice and Home affairs (JHA). The supranational institutions - the Commission, the European Parliament and the Court of Justice had been established through the EC pillar grounded from the treaty.  The CFSP and JHA are based on the cooperation among governments of Member States. By constituting the Three Pillars, there has been the great development in various fields and it has extended the existing policies.
In the first pillar, the European Community has obtained more extension in powers and the institutions of European Union have been more increase in their competences. The Parliament has been expanded its roles through the Maastricht Treaty which emphasizes on the cooperation procedure and the assent procedure. The codecision procedure between the European Parliament and the Council has been allowed to reach agreement; Parliament became for the first time an equal partner in the legislative process, particularly a few crucial areas - transport, environment and consumer protection. Including, the supervisory power was substantially allowed to Parliament. Greater capabilities have been increased in the Court of Justice, the Court of Auditors and the Economic and Social Committee. There have been the denominations of institutions: the Council of the European Union has been the official name of the Ministers Council and the Commission of the European Communities (EC) is derived from the Commission. The new establishment was a Committee of the Regions, and the representatives of the regional authorities have been appointed.4 These institutions are aimed to pursue its centrally economic and political ambitions.
More efficiency has been forming into the areas of foreign and jurisdiction among European Union. Looking into the foreign affair into the second pillar, the treaty has encouraged the coordination in foreign policy, immigration and other matters through the Common Foreign and Security Policy. According to Article11, the aims of the CFSP included the preservation of peace and the strengthening of international security, the promotion of international cooperation, the development and consolidation of democracy and the rule of law, and respect for human rights and fundamental freedoms. It has replaced the provisions of the Single European Act and allows Member States to take joint action in the field of foreign policy. In the area of jurisdiction of the third pillar, the harmonization has been occurred in military, criminal justice and judicial cooperation areas. The foundation of the European Police Office (Europol) was one the most outstanding changes. It has led to The Schengen Convention in which the Schengen Agreement has been developed and was signed to allow the European Union becoming a borderless region. Unanimity from the intergovernmental decision-making process is involved in these two pillars.
The treaty has brought important changes on European economy. The great stage was further to the Economic and Monetary Union (EMU). The European Economic Community has been carried on through the pillar of European Community. Each internal markets of Member states has become a common market -free of tariffs on imports and free movement of goods, services, labour and capital.10 The prominent one, the creation of the Euro currency had been led by this treaty by providing three successive stages. In the first stage, the movement of capital was to be liberalized.12 The convergence of the Member States' economic policies was the second stage.12 The last stage was the creation of a single currency and the establishment of a European Central Bank (ECB), fixing of exchange rates and introduction of a single currency.10 11 member countries have adopted the Euro in their territories. By these institutions and policies, the economy among European member countries has become more integrated, effective and efficient.
The development of society among EU nations has been initiated through the Maastricht treaty. Six new Community policies - industrial policy, trans-European networks and transport policy, consumer protection, educational and vocational training networks, youth and culture - has been established Several programs on educational affairs have been launched - Socrates, Erasmus and Leonardo da Vinci - to benefit European students and teachers. In addition, there has been the social protocol added to the Treaty. The objectives are promotion of employment, improvement of living and working conditions, adequate social protection, social dialogues, sustainable employment and integration of persons excluded from the labor market.14 By the social policies annexed in the treaty, the European citizens have been greatly received the advantage from various programs. The search of social and economic cohesion among the diverse regions and countries of the community are instituted as one of the objectives of Union in the treaty of Maastricht.9 In 1994, a dominated Cohesion fund was agreed to provide the financial aid on environment or transport infrastructures to less developed regions and countries. The eligible applicants are those whose GDP per capita was inferior to 90% of the Union average and comply with convergence criteria.
A national citizen of Member States is also regard as a citizen of the Union. The treaty has led the innovation through the introduction of European creation of European citizenship. Being as a EU citizen, there are the rights, for example, which are the right to circulate and reside freely in the Community and the right to vote and to stand as a candidate for European and municipal elections in the State in which he or she resides.
The enlargement of the Union has been presented in the treaty. The candidates to EU accession were - Austria in 1989, Malta and Cyprus in 1991 and Finland in 1992. The enlargement took place in 1995 with the accession of Austria, Finland and Sweden. The Europe of the Fifteen was born.
By the success of the treaty, the elaboration of new treaty has been introduced which amended from the Treaty of Maastricht. The focus areas were developing the Europe of citizens, fomenting the EU role in international politics, reforming the institutions and tackling a new enlargement to the applicant countries of Central and Eastern Europe. In 1997, the Treaty of Amsterdam was born to fulfill the objectives. 
The greatest progress of European integration has been achieved through the Maastricht treaty. Cooperation among Member States in areas of political, monetary, economic and social has been occurred by the implementation of policies and practices stated on the Treaty. As we can see nowadays each European members are ................
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