There are four main theoretical issues in sociology: validity, reliability, representativeness, and methodological perspective. Validity refers to obtaining an accurate picture of society, while reliability means replicable results. Representativeness means studying a typical cross-section. Methodological perspective influences method choice, with positivists preferring quantitative data to find patterns and interpretivists preferring qualitative data to understand meanings. Constraints like time, resources, access, and consent also influence which methods sociologists can use to study their topics.