This method of reasoning was developed by Aristotle. It uses general principles to predict specific results. Deductive reasoning starts from a general principle or theory, and then collects data, finally analyse and interpret. So this type of reasoning is also called as theory-data collection-analysis method. Deductive method is more widely used and considered more efficient than inductive method.
All living organisms are made up of cells (a generalisation)
Elephant is an a living organism (minor premise)
Therefore elephant is made up of cells (conclusion).
Metals conduct electricity
Silver is a metal
Therefore, silver conducts electricity.
This method was practised by Francis Bacon. Here specific observations are used to construct general scientific principles, just the reverse of deductive method. Inductive reasoning begins with specific observations and then analysis of data leading to the formulation of a general principle. So this type of reasoning is also called as data collection-analysis method. Specific observations that are uniform in result lead to generalisation.
Mango tree is made up of cells
Jack fruit tree is made up of cells
Pinus is made up of cells
Therefore all plants are made up of cells.
In inductive reasoning the correctness or authenticity of the generalised principle depends on the number of specific observation.
This method was proposed by Dutch Physicist Christian Huygens (1629). Hypothetico-deductive method starts with hypothesis formulation from generalised principles or theory. This hypothesis is subjected to verification by deduction and comparison with available data. Then the hypothesis is further tested by series of step by step procedure finally leading to either adoption of rejection of formulated hypothesis. This is similar to the steps involved in a scientific method. The hypothesis will be analysed till the end before it is accepted or rejected.