a) Democracy implies popular sovereignty. Suffrage must be universal. Every individual has the right to take part in constituting and conditioning the government. It is popular sovereignty.
b) The laws of the state affect invariably every one in the state, therefore it is natural that every body expects to have a say in the politics and laws of the government. 'What touches all must be decided by all'.
c) If the suffrage is restricted to a particular class, the government thus constituted with their representatives would tend to protect only their interest, at the expense of the unrepresented sections.
d) Universal suffrage is essential for the development of the individual. Deprival of the right to vote to one section of the society may make that group, as inferior, and the section, which has voting right, may feel superior. Right to vote enhances the opportunity for self - expression in public affairs.
Firstly, the most important demerit of universal adult suffrage is, it opens the gate for all. Those who have no knowledge of government or even who is governing them, are made to vote, to put this in simple terms, the ignorant man votes to elect the leaders.
Secondly, in countries like India, where the ration of literacy is very low, voters are largely illiterates, who cannot even read the names of the candidates but cast their votes by identifying the symbols.
Thirdly, political parties, mostly copitalize on the parochial attitudes of the voters. They field candidates only on the basis of caste. Political leaders appeal not to the nationality of the individuals but to the sentiments of the voters. Masses tend to be carried away by these sentimental appeals.
Fourthly, the electorate being ignorant of national problems and issues choose parties which appeal to their local issues.