# Syntactic Models

## Hypothetico-Deductive Account

A theory is confirmed if observation statements deduced from it are found to be true. (Consequence Condition) If a theory is confirmed, its consequences are also confirmed. (Converse Consequence Condition)

### Problems

#### Conjunction Problem

(A and B) implies, and is thus confirmed by, A. It also implies B, so B is confirmed by the observation of A, whatever A and B are.

#### Disjunction Problem

B implies (A or B). (A or B) is verified by the observation of A. So B is confirmed by the observation of A, whatever A and B are.

## Nicod's Criterion

For statements of the form "All A are B" observations fall into three categories. Observations of As that are Bs confirm, observations of As that are not Bs disconfirm, and observations of things that are not As are irrelevant.

### Problems

The main problem is the Raven Paradox.

## Popperian Refutationism

Popper's theories can be seen as an attempt to provide a syntactic description of induction.